Question

iodine + oxygen
magnesium + nitrogen
aluminum + chlorine
iron + oxygen
calcium + chlorine
nitrogen + bromine
the first electron shell can hold up to ____ electrons.
what 2 elements are in the...?
how many valence electrons does helium have?

Explanation:

Step1: Determine 1st shell capacity

The first electron shell follows the formula $2n^2$ where $n=1$.
$2(1)^2 = 2$

Step2: Find helium's valence electrons

Helium has an atomic number of 2, so all electrons are valence electrons in its full first shell.
Valence electrons = 2

Step3: Write Fluorine + Oxygen formula

Fluorine (F, -1 charge) and Oxygen (O, -2 charge) form covalent compound: $\text{OF}_2$ (Oxygen difluoride)

Step4: Write Magnesium + Nitrogen formula

Magnesium (Mg, +2 charge) and Nitrogen (N, -3 charge): Cross charges to get $\text{Mg}_3\text{N}_2$

Step5: Write Aluminum + Chlorine formula

Aluminum (Al, +3 charge) and Chlorine (Cl, -1 charge): Cross charges to get $\text{AlCl}_3$

Step6: Write Iron + Oxygen formula

Iron(III) (Fe, +3 charge) and Oxygen (O, -2 charge): Cross charges to get $\text{Fe}_2\text{O}_3$ (common iron oxide)

Step7: Write Calcium + Chlorine formula

Calcium (Ca, +2 charge) and Chlorine (Cl, -1 charge): Cross charges to get $\text{CaCl}_2$

Step8: Write Nitrogen + Bromine formula

Nitrogen (N, -3 charge) and Bromine (Br, -1 charge) form covalent compound: $\text{NBr}_3$ (Nitrogen tribromide)

Step9: Identify first period elements

First period elements are Hydrogen (H) and Helium (He)

Answer:

1. The first ELECTRON SHELL can hold up to $\boldsymbol{2}$ electrons.
2. Helium has $\boldsymbol{2}$ valence electrons.
3. Fluorine + Oxygen: $\boldsymbol{\text{OF}_2}$ (Oxygen difluoride)
4. Magnesium + Nitrogen: $\boldsymbol{\text{Mg}_3\text{N}_2}$ (Magnesium nitride)
5. Aluminum + Chlorine: $\boldsymbol{\text{AlCl}_3}$ (Aluminum chloride)
6. Iron + Oxygen: $\boldsymbol{\text{Fe}_2\text{O}_3}$ (Iron(III) oxide)
7. Calcium + Chlorine: $\boldsymbol{\text{CaCl}_2}$ (Calcium chloride)
8. Nitrogen + Bromine: $\boldsymbol{\text{NBr}_3}$ (Nitrogen tribromide)
9. First period elements: Hydrogen (H) and Helium (He)