Atomic structure and the periodic table

Written by Dr. Ayesha Nadeem (Chemistry)

MDCAT · Chemistry · 8 questions

Name: ____________________ Date: ____________

How many electrons does a chloride ion (Cl-) have? (Atomic number of chlorine is 17.)
- A 16
- B 17
- C 19
- D 18
Which element has the highest electronegativity?
- A Oxygen
- B Fluorine
- C Chlorine
- D Nitrogen
The electronic configuration 1s2 2s2 2p6 3s2 belongs to:
- A Aluminium
- B Neon
- C Magnesium
- D Sodium
Which quantum number describes the shape of an orbital?
- A Spin quantum number (s)
- B Principal quantum number (n)
- C Magnetic quantum number (m)
- D Azimuthal quantum number (l)
Across a period from left to right, the atomic radius generally:
- A Stays the same
- B Decreases
- C First decreases, then doubles
- D Increases
How many neutrons are in an atom of carbon-14? (Atomic number 6.)
- A 7
- B 8
- C 6
- D 14
The sodium ion (Na+) has the same electronic configuration as which noble gas?
- A Krypton
- B Helium
- C Neon
- D Argon
What is the maximum number of electrons that a 3d subshell can hold?
- A 2
- B 6
- C 10
- D 14

Answer key

1. D, 2. B, 3. C, 4. D, 5. B, 6. B, 7. C, 8. C

A chlorine atom has 17 electrons. Gaining one electron to form Cl- gives 18.
Fluorine is the most electronegative element, with a value of about 4.0 on the Pauling scale.
The electrons add up to 12, which is the atomic number of magnesium.
The azimuthal quantum number l sets the shape: l = 0 is s, l = 1 is p, l = 2 is d.
The nuclear charge rises while electrons are added to the same shell, so the nucleus pulls the electrons in more strongly.
Neutrons = mass number minus atomic number = 14 - 6 = 8.
Sodium has 11 electrons. Na+ has 10, the same as neon.
A d subshell has five orbitals and each holds two electrons, so the maximum is 10.