Question

1. write the chemical formula for a compound that is made of one atom of carbon (c) and four atoms of hydrogen (h).
2. write the chemical formula for a compound that has two atoms of nitrogen and four atoms of oxygen.

ion: an atom or a group of atoms that has an electrical charge, either positive or negative
when elements form compounds, they become more stable. as you have learned, the noble gases rarely form compounds because they already have a stable electron - shell structure—their outer electron shell is full. all the other elements achieve this full, stable electron - shell structure in one of three ways:

1. metals lose electrons to form positive ions.
2. non - metals gain electrons to form negative ions.
3. non - metals share electrons.
4. helium, like other noble gases, has a full, and therefore stable, outermost electron shell structure. how many electrons are in heliums outermost shell? what about the other noble gas elements? why is there a difference?

Explanation:

Step1: Determine formula for carbon - hydrogen compound

The compound has 1 carbon and 4 hydrogens, so the formula is $CH_4$.

Step2: Determine formula for nitrogen - oxygen compound

The compound has 2 nitrogens and 4 oxygens, so the formula is $N_2O_4$.

Step3: Answer question about helium electrons

Helium has 2 electrons in its outermost shell. Other noble - gas elements (except helium) have 8 electrons in their outermost shell. The difference is because helium has only the first electron shell which can hold a maximum of 2 electrons, while other noble gases have more than one electron shell and the outermost shell (valence shell) can hold 8 electrons to be stable according to the octet rule.

Answer:

1. $CH_4$
2. $N_2O_4$
3. Helium has 2 electrons in its outermost shell. Other noble - gas elements (except helium) have 8 electrons in their outermost shell. The first shell of helium can hold a maximum of 2 electrons while other noble gases' outermost shells follow the octet rule (8 electrons for stability).