Atomic Orbitals and Electronic Configurations

Atomic Structure

Define a quantum shell.

The energy level of an electron in an atom.

Where are quantum shells located?

Around the nucleus of an atom.

Which quantum shell has the lowest energy?

The first quantum shell.

How does the energy of quantum shells generally change with distance from the nucleus?

The energy increases as the distance from the nucleus increases.

What are quantum shells divided into?

Sub-shells.

What are the four types of sub-shell?

s, p, d and f.

Which sub-shell is present in the first quantum shell?

1s.

Which sub-shells are present in the second quantum shell?

2s and 2p.

Which sub-shells are present in the third quantum shell?

3s, 3p and 3d.

Which sub-shells are present in the fourth quantum shell?

4s, 4p, 4d and 4f.

Within the second shell, which has higher energy: 2s or 2p?

2p.

Within the third shell, what is the increasing energy order of the sub-shells?

3s < 3p < 3d.

Within the fourth shell, what is the increasing energy order of the sub-shells?

4s < 4p < 4d < 4f.

Define an atomic orbital.

A region within an atom that can hold up to two electrons with opposite spins.

What is the maximum number of electrons in one orbital?

2.

What must be true of two electrons occupying the same orbital?

They must have opposite spins.

What does an orbital represent?

A region of space where there is a high probability of finding an electron.

Approximately what probability of finding an electron is represented by the boundary of an orbital?

About 90%.

What shape is an s orbital?

Spherical.

Do 1s and 2s orbitals have the same basic shape?

Yes, both are spherical.

How does a 2s orbital compare in size with a 1s orbital?

The 2s orbital is larger.

How many orbitals are in an s sub-shell?

1.

What is the maximum number of electrons in an s sub-shell?

2.

What shape is a p orbital?

An elongated dumbbell shape.

How many p orbitals are in a p sub-shell?

3.

What are the three p orbitals called?

pₓ, pᵧ and p₂.

What is the difference between pₓ, pᵧ and p₂ orbitals?

They have the same shape but different orientations in space.

How are the three p orbitals arranged relative to each other?

At mutual right angles.

What is the maximum number of electrons in a p sub-shell?

6.

How many orbitals are in a d sub-shell?

5.

What is the maximum number of electrons in a d sub-shell?

10.

Do you need to know the detailed shapes of d orbitals at this level?

No.

How many orbitals are in an f sub-shell?

7.

What is the maximum number of electrons in an f sub-shell?

14.

How many orbitals are in an s sub-shell and how many electrons can it hold?

1 orbital and 2 electrons.

How many orbitals are in a p sub-shell and how many electrons can it hold?

3 orbitals and 6 electrons.

How many orbitals are in a d sub-shell and how many electrons can it hold?

5 orbitals and 10 electrons.

How many orbitals are in an f sub-shell and how many electrons can it hold?

7 orbitals and 14 electrons.

What is the maximum number of electrons in the first quantum shell?

2.

What is the maximum number of electrons in the second quantum shell?

8.

What is the maximum number of electrons in the third quantum shell?

18.

What is the maximum number of electrons in the fourth quantum shell?

32.

What are the maximum electron capacities of the first four quantum shells?

2, 8, 18 and 32.

Define electronic configuration.

The distribution of electrons among the atomic orbitals of an atom.

What determines many of the chemical properties of an element?

Its electronic configuration.

How are electrons placed into orbitals in the ground state?

They occupy the lowest available energy orbitals first.

Define the Aufbau principle.

Electrons are added to orbitals in order of increasing energy, starting with the lowest-energy orbital.

What is the general filling order of orbitals up to 4p?

1s → 2s → 2p → 3s → 3p → 4s → 3d → 4p.

Which fills first in potassium and calcium: 4s or 3d?

4s.

Why does 4s fill before 3d in potassium and calcium?

The 4s orbital is lower in energy than the 3d orbitals in these atoms.

What is the electronic configuration of hydrogen?

1s¹.

What is the electronic configuration of helium?

1s².

What is the electronic configuration of lithium?

1s² 2s¹.

What is the electronic configuration of beryllium?

1s² 2s².

What is the electronic configuration of boron?

1s² 2s² 2p¹.

What is the electronic configuration of carbon?

1s² 2s² 2p².

What is the electronic configuration of nitrogen?

1s² 2s² 2p³.

What is the electronic configuration of oxygen?

1s² 2s² 2p⁴.

What is the electronic configuration of fluorine?

1s² 2s² 2p⁵.

What is the electronic configuration of neon?

1s² 2s² 2p⁶.

What is the electronic configuration of sodium?

1s² 2s² 2p⁶ 3s¹.

What is the electronic configuration of magnesium?

1s² 2s² 2p⁶ 3s².

What is the electronic configuration of aluminium?

1s² 2s² 2p⁶ 3s² 3p¹.

What is the electronic configuration of silicon?

1s² 2s² 2p⁶ 3s² 3p².

What is the electronic configuration of phosphorus?

1s² 2s² 2p⁶ 3s² 3p³.

What is the electronic configuration of sulfur?

1s² 2s² 2p⁶ 3s² 3p⁴.

What is the electronic configuration of chlorine?

1s² 2s² 2p⁶ 3s² 3p⁵.

What is the electronic configuration of argon?

1s² 2s² 2p⁶ 3s² 3p⁶.

What is the electronic configuration of potassium?

1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹.

What is the electronic configuration of calcium?

1s² 2s² 2p⁶ 3s² 3p⁶ 4s².

Why is the electronic configuration of potassium not 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹?

The 4s orbital is lower in energy than the 3d orbitals in potassium, so the electron enters 4s first.

Why does calcium have 4s² rather than 3d²?

The 4s orbital is lower in energy than the 3d orbitals in calcium.

What happens to the relative energies of 3d and 4s after calcium?

The 3d orbitals become lower in energy than the 4s orbital.

When transition metals ionise, which electrons are generally lost first: 4s or 3d?

The 4s electrons are lost first.

What is the electronic configuration of scandium?

1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹ 4s².

What is the electronic configuration of titanium?

1s² 2s² 2p⁶ 3s² 3p⁶ 3d² 4s².

What is the electronic configuration of vanadium?

1s² 2s² 2p⁶ 3s² 3p⁶ 3d³ 4s².

What is the electronic configuration of chromium?

1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁵ 4s¹.

What is unusual about the electronic configuration of chromium?

It has 3d⁵ 4s¹ rather than the expected 3d⁴ 4s².

What is the electronic configuration of manganese?

1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁵ 4s².

What is the electronic configuration of iron?

1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁶ 4s².

What is the electronic configuration of cobalt?

1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁷ 4s².

What is the electronic configuration of nickel?

1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁸ 4s².

What is the electronic configuration of copper?

1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s¹.

What is unusual about the electronic configuration of copper?

It has 3d¹⁰ 4s¹ rather than the expected 3d⁹ 4s².