Which element in period 4 would have chemical properties similar to magnesium? 7. which metalloids would have chemical properties similar to bromine? 8. which nonmetal would have chemical properties similar to tin? 9. which element in period 6 would have chemical properties similar to nitrogen? 10. which element is in period 1, group 18? helium?

6) Answer is: calcium (Ca).

Magnesium and calcium are in the group 2 of Periodic table. They have same number of valence electrons (two) and similar chemical properties.

Atomic number of magnesium (Mg) is 12, it means that it has 12 protons and 12 electrons.  

Electron configuration of magnesium atom: ₁₂Mg 1s² 2s² 2p⁶ 3s².

Atomic number of calcium is 20, it means that it has 20 protons and 20 electrons, so atom of calcium is neutral.

Electron configuration of calcium atom: ₂₀Ca 1s² 2s² 2p⁶ 3s² 3p⁶ 4s².

7) Answer is: astatine (At).

Bromine (Br) and astatine are in group 17 of Periodic table. They have same number of valence electrons (seven) and similar chemical properties.

In VIIA or group 17 (halogen elements) there are six elements: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), astatine (At) and tennessin(Ts).

Astatine is a chemical element with symbol At and atomic number 85, it has 85 protons and 85 electrons. Valence electrons are in 6s and 6p orbitals.

Electron configuration of astatine atom: ₈₅At [Xe] 4f¹⁴ 5d¹⁰ 6s² 6p⁵.

8) Answer is: carbon (C).

Tin (Sn) and carbon (C) are in group 14 of Periodic table. They have same number of valence electrons (four) and similar chemical properties.

Carbon  is a chemical element with symbol C and atomic number 6, which means it has 6 protons and six electrons. Valence electrons are in 2s and 2p orbitals.

Electron configuration of carbon atom: ₆C 1s² 2s² 2p².

9) Answer is: bizmuth (Bi).

Nitrogen (N) and bizmuth are in group 15 of Periodic table. They have same number of valence electrons (five) and similar chemical properties.

Bizmuth (Bi) has atomic number 83, it has 83 protons and 83 electrons. Valence electrons are in 6s and 6p orbitals.

Electron configuration of bizmuth atom: ₈₃Bi [Xe] 4f¹⁴ 5d¹⁰ 6s² 6p³.

Electron configuration for nitrogen: ₇N 1s² 2s² 2p³.

10) Answer is: helium (He).

Helium has atomic number 2, it has 2 protons and 2 electrons.

Electron configuration of helium atom: ₂He 1s².

Noble gases (group 18) are in group 18: helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe) and radon (Rn). They have very low chemical reactivity.

Noble gases have very stable electron configuration and does not need to gain electrons, only when they gain energy.