Which pair of elements has atoms with the same number of valence electrons?
1. potassium (K) and bromine (Br)
2. astatine (At) and radon (Rn)
3. indium (In) and lead (Pb)
4. silicon (Si) and germanium (Ge)
4. silicon (Si) and germanium (Ge)
The correct pair of elements with atoms having the same number of valence electrons is option 3. Indium (In, atomic number 49) and lead (Pb, atomic number 82) both have 5 valence electrons.
To determine which pair of elements has atoms with the same number of valence electrons, we need to identify the number of valence electrons for each element in the pairs.
1. Potassium (K) is in group 1 of the periodic table, so it has 1 valence electron.
Bromine (Br) is in group 17, so it has 7 valence electrons.
Therefore, potassium (K) and bromine (Br) do not have the same number of valence electrons.
2. Astatine (At) is in group 17, so it has 7 valence electrons.
Radon (Rn) is in group 18, so it also has 8 valence electrons.
Therefore, astatine (At) and radon (Rn) do not have the same number of valence electrons.
3. Indium (In) is in group 13, so it has 3 valence electrons.
Lead (Pb) is in group 14, so it also has 4 valence electrons.
Therefore, indium (In) and lead (Pb) do not have the same number of valence electrons.
4. Silicon (Si) is in group 14, so it has 4 valence electrons.
Germanium (Ge) is also in group 14, so it also has 4 valence electrons.
Therefore, silicon (Si) and germanium (Ge) have the same number of valence electrons.
Thus, the correct answer is option 4. Silicon (Si) and germanium (Ge) have atoms with the same number of valence electrons.