Question

1. what is the term for the columns going down the periodic table? what is similar for all atoms in the same column (except for the transition metals)?
2. how can you use the periodic table to determine the number of valence electrons?
3. how do you calculate the number of core electrons (these are all the electrons that aren’t valence electrons)?
4. what are the names of the first and last element in period 3?
5. what are the names of the first and last element in group 2?

Explanation:

1. The columns in the periodic table are called groups or families. For non - transition metals in the same group, the number of valence electrons is the same.
2. For main - group elements, the group number (using the old 1 - 8A numbering system) is equal to the number of valence electrons.
3. The number of core electrons is calculated by subtracting the number of valence electrons from the total number of electrons (which is equal to the atomic number for a neutral atom).
4. The first element in period 3 is sodium (Na) and the last is argon (Ar).
5. In group 2 (alkaline earth metals), the first element is beryllium (Be) and as of now, the last naturally - occurring element is radium (Ra).

Answer:

1. Groups or families; number of valence electrons (for non - transition metals)
2. For main - group elements, use the group number (old 1 - 8A system)
3. Total electrons (atomic number for neutral atom) minus valence electrons
4. Sodium (Na), Argon (Ar)
5. Beryllium (Be), Radium (Ra)