Atoms of two adjacent elements in the third period are in the ground state. An atom of element A has only s electrons in its valence shell. An atom of element B has at least one p electron in its vale

Atoms of two adjacent elements in the third period are in the ground state. An atom of element A has only s electrons in its valence shell. An atom of element B has at least one p electron in its valence shell. Identify elements A and B.