Final answer:
Core electrons in periods 1, 2, and 3 are non-valence, interior electrons that reside in energy levels below the valence shell, except in period 1 where only valence electrons are present for hydrogen and helium(option c).
Step-by-step explanation:
The question concerns the nature of core electrons in periods 1, 2, and 3 of the periodic table. Core electrons are defined as the electrons that are not in the outermost energy level of an atom. They are inner electrons that do not typically participate in bonding or chemical reactions. Core electrons provide shielding and can affect the size of the atom and the energy required to remove an electron.
To answer the question about what is true about core electrons in periods 1, 2, and 3:
- (a) They are not valence electrons. Valence electrons are located in the atom's outermost energy level.
- (b) They are not found in the outermost energy level. This is the domain of the valence electrons.
- (c) They are non-valence, interior orbitals. Core electrons are located in the energy levels below the valence shell.
- (d) This statement is false. In period 1, there are no core electrons because the elements hydrogen and helium only have electrons in their outermost shell, which are the valence electrons. However, in periods 2 and 3, core electrons do exist as the 1s orbital electrons for period 2 elements, and both 1s and 2s (and for some, 2p) orbital electrons for period 3 elements.
Therefore, the correct answer is (c) They are non-valence, interior orbitals.