This question tests your understanding of why and how atoms form ions by losing or gaining electrons to achieve stable electron configurations like those of noble gases. Atoms form ions to achieve stable electron configurations, typically matching the nearest noble gas (helium, neon, argon) which have full outer electron shells: metals (left side of periodic table, groups 1-3) form positive ions (cations) by LOSING their few valence electrons, leaving them with a full inner shell matching the previous noble gas. Nonmetals (right side, groups 15-17) form negative ions (anions) by GAINING electrons to complete their outer shells and match the next noble gas. For example, sodium (11 electrons, configuration ending in 3s¹) loses that 1 outer electron to form Na⁺ with 10 electrons, matching neon's stable configuration. Chlorine (17 electrons, ending in 3p⁵, needs 1 more for full octet) gains 1 electron to form Cl⁻ with 18 electrons, matching argon's configuration. The drive toward noble gas stability—full outer shells—explains why specific charges form! Aluminum has atomic number 13, so a neutral atom has 13 electrons; to form Al³⁺, it loses 3 electrons, resulting in 10 electrons and a configuration matching neon (1s² 2s² 2p⁶). Choice B correctly explains ion formation by identifying that electrons are lost and connecting this to achieving stable noble gas configuration. Choice A fails because it suggests aluminum gains electrons, forming a negative ion, but group 13 metals lose three electrons to form +3 ions. The ion charge prediction recipe from periodic table: (1) Identify group number: Groups 1, 2, 13 are metals that LOSE electrons. Groups 15, 16, 17 are nonmetals that GAIN electrons. (2) Predict charge from group: Group 1 loses 1 → forms +1. Group 2 loses 2 → forms +2. Group 13 loses 3 → forms +3. Group 15 gains 3 → forms -3. Group 16 gains 2 → forms -2. Group 17 gains 1 → forms -1. The pattern: for metals, positive charge equals group number (mostly). For nonmetals, negative charge equals 8 minus group number (to reach 8 valence). (3) Verify with noble gas: Which noble gas is nearest? Metals lose to match previous noble gas (sodium matches neon by losing 1). Nonmetals gain to match next noble gas (chlorine matches argon by gaining 1). This method predicts common ions reliably! Electron bookkeeping for ions: if atom has 11 electrons and forms +1 ion, it LOST 1 electron, leaving 10. If atom has 17 electrons and forms -1 ion, it GAINED 1 electron, giving 18. The math: ion electrons = atomic number - charge. For Na⁺: 11 - (+1) = 10 electrons. For Cl⁻: 17 - (-1) = 18 electrons (subtracting negative adds!). For Mg²⁺: 12 - (+2) = 10 electrons. Quick check: cations should have fewer electrons than protons (positive charge makes sense), anions should have more electrons than protons (negative charge makes sense). If your ion doesn't match this, recheck your electron counting! Impressive work—ions are your strength now!

This question tests your understanding of why and how atoms form ions by losing or gaining electrons to achieve stable electron configurations like those of noble gases. Atoms form ions to achieve stable electron configurations, typically matching the nearest noble gas (helium, neon, argon) which have full outer electron shells: metals (left side of periodic table, groups 1-3) form positive ions (cations) by LOSING their few valence electrons, leaving them with a full inner shell matching the previous noble gas. Nonmetals (right side, groups 15-17) form negative ions (anions) by GAINING electrons to complete their outer shells and match the next noble gas. For nitrogen (N, atomic number 7, electron configuration 1s² 2s² 2p³), it gains 3 electrons to fill its 2p orbital, resulting in N³⁻ with 10 electrons and the configuration 1s² 2s² 2p⁶, matching neon's stable octet—terrific progress in mastering ion stability! Choice A correctly explains ion formation by identifying that nitrogen gains 3 electrons to achieve the stable neon configuration, forming N³⁻. Choice B fails because nitrogen, as a nonmetal, gains electrons rather than losing them, and losing would form a positive ion, not N³⁻; choices C and D suggest gaining or losing 5, which wouldn't achieve an octet or match neon. The ion charge prediction recipe from periodic table: (1) Identify group number: Groups 1, 2, 13 are metals that LOSE electrons. Groups 15, 16, 17 are nonmetals that GAIN electrons. (2) Predict charge from group: Group 1 loses 1 → forms +1. Group 2 loses 2 → forms +2. Group 13 loses 3 → forms +3. Group 15 gains 3 → forms -3. Group 16 gains 2 → forms -2. Group 17 gains 1 → forms -1. The pattern: for metals, positive charge equals group number (mostly). For nonmetals, negative charge equals 8 minus group number (to reach 8 valence). (3) Verify with noble gas: Which noble gas is nearest? Metals lose to match previous noble gas (sodium matches neon by losing 1). Nonmetals gain to match next noble gas (chlorine matches argon by gaining 1). This method predicts common ions reliably! Electron bookkeeping for ions: if atom has 11 electrons and forms +1 ion, it LOST 1 electron, leaving 10. If atom has 17 electrons and forms -1 ion, it GAINED 1 electron, giving 18. The math: ion electrons = atomic number - charge. For Na⁺: 11 - (+1) = 10 electrons. For Cl⁻: 17 - (-1) = 18 electrons (subtracting negative adds!). For Mg²⁺: 12 - (+2) = 10 electrons. Quick check: cations should have fewer electrons than protons (positive charge makes sense), anions should have more electrons than protons (negative charge makes sense). If your ion doesn't match this, recheck your electron counting!

This question tests your understanding of why and how atoms form ions by losing or gaining electrons to achieve stable electron configurations like those of noble gases. Atoms form ions to achieve stable electron configurations, typically matching the nearest noble gas (helium, neon, argon) which have full outer electron shells: metals (left side of periodic table, groups 1-3) form positive ions (cations) by LOSING their few valence electrons, leaving them with a full inner shell matching the previous noble gas. Nonmetals (right side, groups 15-17) form negative ions (anions) by GAINING electrons to complete their outer shells and match the next noble gas. For chlorine (Cl, atomic number 17, electron configuration 1s² 2s² 2p⁶ 3s² 3p⁵), it gains 1 electron to fill its 3p orbital, resulting in Cl⁻ with 18 electrons and the configuration 1s² 2s² 2p⁶ 3s² 3p⁶, matching argon's stable octet—excellent work seeing how this completes the shell! Choice B correctly explains ion formation by identifying that chlorine gains 1 electron to achieve the stable argon configuration, forming Cl⁻. Choice A fails because chlorine, as a nonmetal, gains electrons rather than losing them, and losing would form a positive ion, not the observed Cl⁻; choices C and D suggest gaining 2 or losing 7, which wouldn't achieve argon's configuration or an octet. The ion charge prediction recipe from periodic table: (1) Identify group number: Groups 1, 2, 13 are metals that LOSE electrons. Groups 15, 16, 17 are nonmetals that GAIN electrons. (2) Predict charge from group: Group 1 loses 1 → forms +1. Group 2 loses 2 → forms +2. Group 13 loses 3 → forms +3. Group 15 gains 3 → forms -3. Group 16 gains 2 → forms -2. Group 17 gains 1 → forms -1. The pattern: for metals, positive charge equals group number (mostly). For nonmetals, negative charge equals 8 minus group number (to reach 8 valence). (3) Verify with noble gas: Which noble gas is nearest? Metals lose to match previous noble gas (sodium matches neon by losing 1). Nonmetals gain to match next noble gas (chlorine matches argon by gaining 1). This method predicts common ions reliably! Electron bookkeeping for ions: if atom has 11 electrons and forms +1 ion, it LOST 1 electron, leaving 10. If atom has 17 electrons and forms -1 ion, it GAINED 1 electron, giving 18. The math: ion electrons = atomic number - charge. For Na⁺: 11 - (+1) = 10 electrons. For Cl⁻: 17 - (-1) = 18 electrons (subtracting negative adds!). For Mg²⁺: 12 - (+2) = 10 electrons. Quick check: cations should have fewer electrons than protons (positive charge makes sense), anions should have more electrons than protons (negative charge makes sense). If your ion doesn't match this, recheck your electron counting!

This question tests your understanding of why and how atoms form ions by losing or gaining electrons to achieve stable electron configurations like those of noble gases. Atoms form ions to achieve stable electron configurations, typically matching the nearest noble gas (helium, neon, argon) which have full outer electron shells: metals (left side of periodic table, groups 1-3) form positive ions (cations) by LOSING their few valence electrons, leaving them with a full inner shell matching the previous noble gas. Nonmetals (right side, groups 15-17) form negative ions (anions) by GAINING electrons to complete their outer shells and match the next noble gas. For magnesium (Mg, atomic number 12, electron configuration 1s² 2s² 2p⁶ 3s²), it loses its 2 valence electrons from the 3s orbital, resulting in Mg²⁺ with 10 electrons and the configuration 1s² 2s² 2p⁶, matching neon's stable structure—keep up the great effort in grasping this! Choice B correctly explains ion formation by identifying that magnesium loses 2 electrons to achieve the stable neon configuration, forming Mg²⁺. Choice A fails because magnesium, as a metal, loses electrons rather than gaining them, and gaining would form a negative ion, not Mg²⁺; choices C and D suggest losing only 1 or involving protons, which doesn't match the group 2 pattern or neon's configuration. The ion charge prediction recipe from periodic table: (1) Identify group number: Groups 1, 2, 13 are metals that LOSE electrons. Groups 15, 16, 17 are nonmetals that GAIN electrons. (2) Predict charge from group: Group 1 loses 1 → forms +1. Group 2 loses 2 → forms +2. Group 13 loses 3 → forms +3. Group 15 gains 3 → forms -3. Group 16 gains 2 → forms -2. Group 17 gains 1 → forms -1. The pattern: for metals, positive charge equals group number (mostly). For nonmetals, negative charge equals 8 minus group number (to reach 8 valence). (3) Verify with noble gas: Which noble gas is nearest? Metals lose to match previous noble gas (sodium matches neon by losing 1). Nonmetals gain to match next noble gas (chlorine matches argon by gaining 1). This method predicts common ions reliably! Electron bookkeeping for ions: if atom has 11 electrons and forms +1 ion, it LOST 1 electron, leaving 10. If atom has 17 electrons and forms -1 ion, it GAINED 1 electron, giving 18. The math: ion electrons = atomic number - charge. For Na⁺: 11 - (+1) = 10 electrons. For Cl⁻: 17 - (-1) = 18 electrons (subtracting negative adds!). For Mg²⁺: 12 - (+2) = 10 electrons. Quick check: cations should have fewer electrons than protons (positive charge makes sense), anions should have more electrons than protons (negative charge makes sense). If your ion doesn't match this, recheck your electron counting!

This question tests your understanding of why and how atoms form ions by losing or gaining electrons to achieve stable electron configurations like those of noble gases. Atoms form ions to achieve stable electron configurations, typically matching the nearest noble gas (helium, neon, argon) which have full outer electron shells: metals (left side of periodic table, groups 1-3) form positive ions (cations) by LOSING their few valence electrons, leaving them with a full inner shell matching the previous noble gas. Nonmetals (right side, groups 15-17) form negative ions (anions) by GAINING electrons to complete their outer shells and match the next noble gas. For example, sodium (11 electrons, configuration ending in 3s¹) loses that 1 outer electron to form Na⁺ with 10 electrons, matching neon's stable configuration. Chlorine (17 electrons, ending in 3p⁵, needs 1 more for full octet) gains 1 electron to form Cl⁻ with 18 electrons, matching argon's configuration. The drive toward noble gas stability—full outer shells—explains why specific charges form! Bromine has atomic number 35, so a neutral atom has 35 electrons; to form Br⁻, it gains 1 electron, resulting in 36 electrons and a configuration matching krypton. Choice A correctly explains ion formation by identifying that electrons are gained and connecting this to achieving stable noble gas configuration. Choice B fails because it suggests bromine loses an electron, forming a positive ion, but group 17 nonmetals gain one electron to form -1 ions. The ion charge prediction recipe from periodic table: (1) Identify group number: Groups 1, 2, 13 are metals that LOSE electrons. Groups 15, 16, 17 are nonmetals that GAIN electrons. (2) Predict charge from group: Group 1 loses 1 → forms +1. Group 2 loses 2 → forms +2. Group 13 loses 3 → forms +3. Group 15 gains 3 → forms -3. Group 16 gains 2 → forms -2. Group 17 gains 1 → forms -1. The pattern: for metals, positive charge equals group number (mostly). For nonmetals, negative charge equals 8 minus group number (to reach 8 valence). (3) Verify with noble gas: Which noble gas is nearest? Metals lose to match previous noble gas (sodium matches neon by losing 1). Nonmetals gain to match next noble gas (chlorine matches argon by gaining 1). This method predicts common ions reliably! Electron bookkeeping for ions: if atom has 11 electrons and forms +1 ion, it LOST 1 electron, leaving 10. If atom has 17 electrons and forms -1 ion, it GAINED 1 electron, giving 18. The math: ion electrons = atomic number - charge. For Na⁺: 11 - (+1) = 10 electrons. For Cl⁻: 17 - (-1) = 18 electrons (subtracting negative adds!). For Mg²⁺: 12 - (+2) = 10 electrons. Quick check: cations should have fewer electrons than protons (positive charge makes sense), anions should have more electrons than protons (negative charge makes sense). If your ion doesn't match this, recheck your electron counting! Superb understanding—you're almost there!

This question tests your understanding of why and how atoms form ions by losing or gaining electrons to achieve stable electron configurations like those of noble gases. Atoms form ions to achieve stable electron configurations, typically matching the nearest noble gas (helium, neon, argon) which have full outer electron shells: metals (left side of periodic table, groups 1-3) form positive ions (cations) by LOSING their few valence electrons, leaving them with a full inner shell matching the previous noble gas. Nonmetals (right side, groups 15-17) form negative ions (anions) by GAINING electrons to complete their outer shells and match the next noble gas. For sulfur (S, atomic number 16, electron configuration 1s² 2s² 2p⁶ 3s² 3p⁴ with 6 valence electrons), it gains 2 electrons to fill its 3p orbital to 8 valence electrons, resulting in S²⁻ with 18 electrons and a configuration matching argon's stable octet—keep building on this strong foundation! Choice A correctly explains ion formation by identifying that sulfur gains 2 electrons to reach a full octet, forming S²⁻. Choice B fails because sulfur, as a nonmetal, gains electrons rather than losing them, and losing would form a positive ion, not S²⁻; choices C and D suggest gaining or losing 6, which misapplies the valence electron count and wouldn't achieve stability. The ion charge prediction recipe from periodic table: (1) Identify group number: Groups 1, 2, 13 are metals that LOSE electrons. Groups 15, 16, 17 are nonmetals that GAIN electrons. (2) Predict charge from group: Group 1 loses 1 → forms +1. Group 2 loses 2 → forms +2. Group 13 loses 3 → forms +3. Group 15 gains 3 → forms -3. Group 16 gains 2 → forms -2. Group 17 gains 1 → forms -1. The pattern: for metals, positive charge equals group number (mostly). For nonmetals, negative charge equals 8 minus group number (to reach 8 valence). (3) Verify with noble gas: Which noble gas is nearest? Metals lose to match previous noble gas (sodium matches neon by losing 1). Nonmetals gain to match next noble gas (chlorine matches argon by gaining 1). This method predicts common ions reliably! Electron bookkeeping for ions: if atom has 11 electrons and forms +1 ion, it LOST 1 electron, leaving 10. If atom has 17 electrons and forms -1 ion, it GAINED 1 electron, giving 18. The math: ion electrons = atomic number - charge. For Na⁺: 11 - (+1) = 10 electrons. For Cl⁻: 17 - (-1) = 18 electrons (subtracting negative adds!). For Mg²⁺: 12 - (+2) = 10 electrons. Quick check: cations should have fewer electrons than protons (positive charge makes sense), anions should have more electrons than protons (negative charge makes sense). If your ion doesn't match this, recheck your electron counting!

This question tests your understanding of why and how atoms form ions by losing or gaining electrons to achieve stable electron configurations like those of noble gases. Atoms form ions to achieve stable electron configurations, typically matching the nearest noble gas (helium, neon, argon) which have full outer electron shells: metals (left side of periodic table, groups 1-3) form positive ions (cations) by LOSING their few valence electrons, leaving them with a full inner shell matching the previous noble gas. Nonmetals (right side, groups 15-17) form negative ions (anions) by GAINING electrons to complete their outer shells and match the next noble gas. For example, sodium (11 electrons, configuration ending in 3s¹) loses that 1 outer electron to form Na⁺ with 10 electrons, matching neon's stable configuration. Chlorine (17 electrons, ending in 3p⁵, needs 1 more for full octet) gains 1 electron to form Cl⁻ with 18 electrons, matching argon's configuration. The drive toward noble gas stability—full outer shells—explains why specific charges form! Sodium (Na) has 11 electrons total: 2 in the first shell, 8 in the second shell, and just 1 lonely electron in the third shell (3s¹). When Na loses this single valence electron, it's left with 10 electrons arranged exactly like neon (Ne): a complete, stable outer shell of 8 electrons. This creates Na⁺ with 11 protons but only 10 electrons, giving the +1 charge. Choice B correctly explains that Na loses 1 valence electron to achieve neon's stable noble-gas configuration, leaving 10 electrons and a +1 charge—this perfectly matches what happens! Choice A incorrectly suggests Na gains an electron to form Na⁻, but metals don't gain electrons—they lose them to expose full inner shells. The ion charge prediction recipe from periodic table: (1) Identify group number: Groups 1, 2, 13 are metals that LOSE electrons. Groups 15, 16, 17 are nonmetals that GAIN electrons. (2) Predict charge from group: Group 1 loses 1 → forms +1. Group 2 loses 2 → forms +2. Group 13 loses 3 → forms +3. Group 15 gains 3 → forms -3. Group 16 gains 2 → forms -2. Group 17 gains 1 → forms -1. The pattern: for metals, positive charge equals group number (mostly). For nonmetals, negative charge equals 8 minus group number (to reach 8 valence). (3) Verify with noble gas: Which noble gas is nearest? Metals lose to match previous noble gas (sodium matches neon by losing 1). Nonmetals gain to match next noble gas (chlorine matches argon by gaining 1). This method predicts common ions reliably!

This question tests your understanding of why and how atoms form ions by losing or gaining electrons to achieve stable electron configurations like those of noble gases. Atoms form ions to achieve stable electron configurations, typically matching the nearest noble gas (helium, neon, argon) which have full outer electron shells: metals (left side of periodic table, groups 1-3) form positive ions (cations) by LOSING their few valence electrons, leaving them with a full inner shell matching the previous noble gas. Nonmetals (right side, groups 15-17) form negative ions (anions) by GAINING electrons to complete their outer shells and match the next noble gas. For oxygen (O, atomic number 8, electron configuration 1s² 2s² 2p⁴), it gains 2 electrons to fill its 2p orbital, resulting in O²⁻ with 10 electrons and the configuration 1s² 2s² 2p⁶, matching neon's stable octet—you're doing wonderfully understanding this process! Choice A correctly explains ion formation by identifying that oxygen gains 2 electrons to achieve the stable neon configuration, forming O²⁻. Choice B fails because oxygen, as a nonmetal, gains electrons rather than losing them, and losing would form a positive ion, not O²⁻; choices C and D suggest gaining 1 or losing 6, which wouldn't complete the octet or match neon. The ion charge prediction recipe from periodic table: (1) Identify group number: Groups 1, 2, 13 are metals that LOSE electrons. Groups 15, 16, 17 are nonmetals that GAIN electrons. (2) Predict charge from group: Group 1 loses 1 → forms +1. Group 2 loses 2 → forms +2. Group 13 loses 3 → forms +3. Group 15 gains 3 → forms -3. Group 16 gains 2 → forms -2. Group 17 gains 1 → forms -1. The pattern: for metals, positive charge equals group number (mostly). For nonmetals, negative charge equals 8 minus group number (to reach 8 valence). (3) Verify with noble gas: Which noble gas is nearest? Metals lose to match previous noble gas (sodium matches neon by losing 1). Nonmetals gain to match next noble gas (chlorine matches argon by gaining 1). This method predicts common ions reliably! Electron bookkeeping for ions: if atom has 11 electrons and forms +1 ion, it LOST 1 electron, leaving 10. If atom has 17 electrons and forms -1 ion, it GAINED 1 electron, giving 18. The math: ion electrons = atomic number - charge. For Na⁺: 11 - (+1) = 10 electrons. For Cl⁻: 17 - (-1) = 18 electrons (subtracting negative adds!). For Mg²⁺: 12 - (+2) = 10 electrons. Quick check: cations should have fewer electrons than protons (positive charge makes sense), anions should have more electrons than protons (negative charge makes sense). If your ion doesn't match this, recheck your electron counting!

This question tests your understanding of why and how atoms form ions by losing or gaining electrons to achieve stable electron configurations like those of noble gases. Atoms form ions to achieve stable electron configurations, typically matching the nearest noble gas (helium, neon, argon) which have full outer electron shells: metals (left side of periodic table, groups 1-3) form positive ions (cations) by LOSING their few valence electrons, leaving them with a full inner shell matching the previous noble gas. Nonmetals (right side, groups 15-17) form negative ions (anions) by GAINING electrons to complete their outer shells and match the next noble gas. For example, sodium (11 electrons, configuration ending in 3s¹) loses that 1 outer electron to form Na⁺ with 10 electrons, matching neon's stable configuration. Chlorine (17 electrons, ending in 3p⁵, needs 1 more for full octet) gains 1 electron to form Cl⁻ with 18 electrons, matching argon's configuration. The drive toward noble gas stability—full outer shells—explains why specific charges form! Chlorine has 17 electrons with configuration ending in 3s²3p⁵—that's 7 valence electrons, just one shy of a complete octet! When Cl gains 1 electron, it fills that last spot in the 3p sublevel (3p⁶), giving it 18 electrons total, exactly matching argon's stable noble gas configuration. This creates Cl⁻ with 17 protons but 18 electrons, producing the -1 charge. Choice A correctly identifies that Cl gains 1 electron to complete its valence shell (3p⁶), achieving argon's stable configuration and forming Cl⁻—this is exactly right! Choice B incorrectly suggests Cl loses an electron to form Cl⁺, but nonmetals like chlorine gain electrons, not lose them—losing would leave Cl with only 6 valence electrons, farther from stability. Electron bookkeeping for ions: if atom has 11 electrons and forms +1 ion, it LOST 1 electron, leaving 10. If atom has 17 electrons and forms -1 ion, it GAINED 1 electron, giving 18. The math: ion electrons = atomic number - charge. For Na⁺: 11 - (+1) = 10 electrons. For Cl⁻: 17 - (-1) = 18 electrons (subtracting negative adds!). For Mg²⁺: 12 - (+2) = 10 electrons. Quick check: cations should have fewer electrons than protons (positive charge makes sense), anions should have more electrons than protons (negative charge makes sense). If your ion doesn't match this, recheck your electron counting!

This question tests your understanding of why and how atoms form ions by losing or gaining electrons to achieve stable electron configurations like those of noble gases. Atoms form ions to achieve stable electron configurations, typically matching the nearest noble gas (helium, neon, argon) which have full outer electron shells: metals (left side of periodic table, groups 1-3) form positive ions (cations) by LOSING their few valence electrons, leaving them with a full inner shell matching the previous noble gas. Nonmetals (right side, groups 15-17) form negative ions (anions) by GAINING electrons to complete their outer shells and match the next noble gas. For example, sodium (11 electrons, configuration ending in 3s¹) loses that 1 outer electron to form Na⁺ with 10 electrons, matching neon's stable configuration. Chlorine (17 electrons, ending in 3p⁵, needs 1 more for full octet) gains 1 electron to form Cl⁻ with 18 electrons, matching argon's configuration. The drive toward noble gas stability—full outer shells—explains why specific charges form! Sulfur, being in group 16, has 6 valence electrons and needs 2 more to complete its octet. When S gains 2 electrons, it goes from 16 to 18 electrons total, achieving the same electron configuration as argon (Ar): a complete outer shell with 8 valence electrons. This creates S²⁻ with 16 protons but 18 electrons, producing the -2 charge. Choice A correctly connects sulfur's group 16 position to its tendency to gain 2 electrons (since 8 - 6 = 2), forming S²⁻ with argon's electron configuration—this perfectly explains the pattern! Choice B incorrectly suggests S loses 6 electrons to form S⁶⁺, but nonmetals gain electrons, and losing 6 would leave sulfur with only 10 electrons (like neon) but would require enormous energy. The ion charge prediction recipe from periodic table: (1) Identify group number: Groups 1, 2, 13 are metals that LOSE electrons. Groups 15, 16, 17 are nonmetals that GAIN electrons. (2) Predict charge from group: Group 1 loses 1 → forms +1. Group 2 loses 2 → forms +2. Group 13 loses 3 → forms +3. Group 15 gains 3 → forms -3. Group 16 gains 2 → forms -2. Group 17 gains 1 → forms -1. The pattern: for metals, positive charge equals group number (mostly). For nonmetals, negative charge equals 8 minus group number (to reach 8 valence). (3) Verify with noble gas: Which noble gas is nearest? Metals lose to match previous noble gas (sodium matches neon by losing 1). Nonmetals gain to match next noble gas (chlorine matches argon by gaining 1). This method predicts common ions reliably!