Question

question 12 (1 point)
the atomic number of an element is the total number of which particles in the nucleus?
o a protons and electrons
b electrons
o c protons
o d neutrons

question 13 (2 points)
what element has the electron configuration 1s²2s²2p⁶3s²3p²?
o a nitrogen
b silicon
o c selenium
d silver

question 14 (1 point)
which of the following is true about the electron configurations of the noble gases?
o a the electrons with the highest energy are in an f sublevel.
b the highest occupied s and p sublevels are partially filled.
o c the highest occupied s and p sublevels are completely filled.
d the electrons with the highest energy are in a d sublevel.

Explanation:

• Question 12: The atomic number of an element is defined as the number of protons in the nucleus of an atom of that element. Electrons are not in the nucleus (they orbit around it), and neutrons contribute to the mass number (protons + neutrons).
• Question 13: To find the element from the electron configuration \(1s^{2}2s^{2}2p^{6}3s^{2}3p^{2}\), calculate the total number of electrons. \(2 + 2+6 + 2+2=14\). The number of electrons in a neutral atom is equal to the atomic number. Silicon has an atomic number of 14. Nitrogen has an atomic number of 7, selenium has 34, and silver has 47.
• Question 14: Noble gases have a full valence shell. The valence shell consists of \(s\) and \(p\) sub - levels. For example, helium (\(1s^{2}\)), neon (\(1s^{2}2s^{2}2p^{6}\)) etc. The highest occupied \(s\) and \(p\) sublevels are completely filled. Electrons in noble gases do not have their highest - energy electrons in \(f\) or \(d\) sublevels (except for some heavier noble gases in excited states, but in the ground state, the general rule is about filled \(s\) and \(p\) for the valence shell).

Answer:

• Question 12: C. protons
• Question 13: B. silicon
• Question 14: C. The highest occupied \(s\) and \(p\) sublevels are completely filled.