Question

1. make a rule: if you knew the number of valence electrons in a nonmetal atom, how would you determine the valence of the element? (hint: ignore hydrogen for now.)
2. analyze: the first shell can hold a maximum of two electrons. how does this explain the valence of hydrogen?
3. apply: selenium has six valence electrons. what is the valence of selenium?
4. think and discuss: the last column of the periodic table contains the noble gases, elements that do not easily form chemical bonds. why dont these gases tend to form chemical bonds?

Explanation:

Step1: Determine valence rule for non - metals

For non - metals (excluding hydrogen), the valence is either equal to the number of valence electrons when forming covalent bonds to gain more electrons, or 8 minus the number of valence electrons when forming ionic or covalent bonds to lose or share electrons to achieve an octet.

Step2: Analyze hydrogen's valence

Hydrogen has 1 valence electron. The first shell can hold a maximum of 2 electrons. So, hydrogen can gain 1 electron to fill its first shell, giving it a valence of 1.

Step3: Find selenium's valence

Selenium has 6 valence electrons. To achieve an octet, it can gain 2 electrons. So its valence is 2.

Step4: Explain noble gases

Noble gases have a full outer - shell of electrons. They have 8 valence electrons (except helium which has 2). Since their outer shells are already stable, they do not tend to form chemical bonds easily.

Answer:

1. The valence of a non - metal (excluding hydrogen) is either the number of valence electrons or 8 minus the number of valence electrons.
2. Hydrogen has 1 valence electron and the first shell can hold 2. It can gain 1 electron, so its valence is 1.
3. 2
4. Noble gases have a full outer - shell of electrons, so they are stable and do not easily form chemical bonds.