First Prep Class Worksheet

The atom is the building unit of the matter

• True

• False

Answer explanation

True. Atoms are the fundamental building blocks of matter, combining to form molecules and all substances in the universe.

Electrons are found inside the nucleus

• True

• False

Answer explanation

Electrons are not found inside the nucleus; they orbit around it in electron shells. The nucleus contains protons and neutrons, making the statement false.

Four main energy levels revolve around the nucleus

• True

• False

Answer explanation

The statement is true because electrons occupy four main energy levels (or shells) around the nucleus of an atom, which are designated as K, L, M, and N. These levels determine the distribution of electrons.

The charge of protons is larger than electrons

• True

• False

Answer explanation

True. Protons have a positive charge of +1, while electrons have a negative charge of -1. The magnitude of the charge of protons is indeed larger than that of electrons, making the statement true.

The chemical symbol of sodium element is S

• True

• False

Answer explanation

The chemical symbol for sodium is actually 'Na', not 'S'. Therefore, the statement is false.

The atomic weight is larger than atomic number for all elements

• True

• False

Answer explanation

The statement is false because the atomic weight of some elements, like hydrogen (atomic number 1), is less than their atomic number. Atomic weight is influenced by isotopes and is not always greater than the atomic number.

The third energy level is saturated with 18 electrons

• True

• False

Answer explanation

The third energy level can hold a maximum of 18 electrons, as it can accommodate 2n² electrons where n=3. Therefore, the statement that it is saturated with 18 electrons is true.

The energy level K is the largest level in energy

• True

• False

Answer explanation

The energy levels in an atom are labeled K, L, M, etc., with K being the lowest energy level. Therefore, the statement is false; K is not the largest level in energy.

The electronic configuration for an element that contains 15 neutrons and 14 protons on three levels

Answer explanation

The element with 14 protons is silicon (Si), atomic number 14. Its electronic configuration is 1s² 2s² 2p⁶ 3s² 3p², which fits within three energy levels.

The outermost energy level of magnesium contains 2 electrons

• True

• False

Answer explanation

True. Magnesium has an atomic number of 12, and its electron configuration is 1s² 2s² 2p⁶ 3s². The outermost energy level (3s) contains 2 electrons.