Orbitals are plots of electron position (90% probability) around the nucleus. They are three dimensional (not planar). An s-orbital is a sphere; a p-orbital is a three dimensional figure-of-eight.

So the answer here that best decribes a p-orbital is .

The blue spherical image represents an s-orbital.

For HL students only: The elongated blue image represents a sigma molecular orbital (two orbitals overlapping end on) and the elongated red image represents a pi molecular orbital (two p-orbitals overlapping side on).

The sub-levels of an atom are filled in the following order: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s. Remember that 's' sub-levels hold a maximum of 2 electrons, 'p' hold 6, and 'd' hold 10. A chromium atom has 24 electrons in total (atomic number is 24), but the configuration is not what would be expected as the six electrons in the 4s and 3d energy levels are all in singly-occupied orbitals (4s¹ 3d⁵) instead of filling the sub-levels in the conventional manner (4s² 3d⁴). Chromium and copper have unusual configurations and need to be learned.

Remember that [Ar] is shorthand and indicates the electron configuration of argon: 1s²2s²2p⁶3s²3p⁶.

The correct answer is therefore 1s² 2s²2p⁶3s²3p⁶4s¹3d⁵

The upper number is the mass number, which is equal to protons plus neutrons. The lower number is the atomic number which is the number of protons. The number of electrons is equal to the number of protons in a neutral atom, but this is 2− negative ion, so it has two more electrons than protons.

So the species has 34 protons, (79−34=) 45 neutrons and 36 electrons (two more than protons).

The line emission spectrum of hydrogen is composed of discrete lines that represent particular frequencies of light. Lines are produced by electron transitions from higher to lower energy levels (for emission; from lower to higher for absorption).

The lines converge at higher frequencies (not lower).

Electron transitions in the hydrogen emission spectrum from higher energy levels to n=1 result in emissions in the ultra-violet region (highest energy since these transitions have the largest gaps between energy levels). Transitions to n=2 are found in the visible region. Transitions to n=3 are found in the infra-red region (lowest energy since these transitions have the smallest gaps between energy levels).

Thus the answer is 1 only.

The upper (superscript) number on the left is the mass number, which is equal to protons plus neutrons. The atomic number for vanadium is 23, which is the number of protons; shown on the periodic table. All atoms of vanadium have the same number of protons. ⁵¹V²⁺ therefore has 51−23=28 neutrons and ⁵⁰V³⁺ has 50−23=27 neutrons.

The number of electrons is equal to the number of protons in a neutral atom, but these species are positive ions so will have more protons than electrons.

The correct answer is therefore Both have the same number of protons.

The upper (superscript) number on the left is the mass number, which is equal to protons plus neutrons. The atomic number, which is the number of protons is shown on the periodic table. The number of electrons is equal to the number of protons in a neutral atom but negative ions will have correspondingly more electrons:

³²S²⁻ has 32−16=16 neutrons and 16+2=18 electrons

³²S has 32−16=16 neutrons and 16 electrons

³¹P³⁻ has 31−15=16 neutrons and 15+3=18 electrons

³¹P has 31−15=16 neutrons and 15 electrons

¹³N³⁻ has 13−7=6 neutrons and 7+3=10 electrons

¹³N has 13−7=6 neutrons and 7 electrons

The correct answer is therefore ³²S²⁻, ³¹P³⁻, ¹³N as this is the only set in which all species contain more electrons than neutrons.

Longer wavelength corresponds to lower frequency/lower energy. So the longest wavelength will correspond to the electron transition of lowest energy.

The question also asks about absorption - energy taken in - so the transition must be from a lower to higher energy level.

The energy gaps between the levels gets smaller at higher energy.

Therefore the smallest energy transition that is also an absorption is n=3 to n=4, which is therefore the correct answer.

The electron configuration reflects an element's position on the periodic table.

The easiest way to solve this is to count the total number of electrons (16); as this is an atom, the number of electrons will be equal to the number of protons, so the element is sulfur.

Sulfur is in Group 16, Period 3.

The upper number is the mass number, which is equal to protons plus neutrons (19 sub-atomic particles in the nucleus). The lower number is the atomic number which is the number of protons. The number of electrons is equal to the number of protons in a neutral atom, but this is a 1− negative ion, so it has one more electron than protons.

So the species has 9 protons, (19−9=)10 neutrons and 10 electrons (1s² 2s² 2p⁶).

The correct answer is therefore Most of the volume of the ion is unoccupied 'space' which is of course the case with all atoms and ions, since most of the mass is concentrated in the nucleus.

The upper number on the left is the mass number, which is equal to protons plus neutrons. The atomic number for rubidium is 37, which is the number of protons; shown on the periodic table.

⁸⁹Rb therefore has 37 protons and (89−37=)52 neutrons.

The correct answer is therefore 37 protons, 52 neutrons.

The sub-levels of an atom are filled in the following order: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s.

Remember that 's' sub-levels hold a maximum of 2 electrons, 'p' hold 6, and 'd' hold 10, and that [Ar] is shorthand and indicates the electron configuration of argon: 1s²2s²2p⁶3s²3p⁶.

A cobalt atom has 27 electrons in total (atomic number is 27) so the condensed atomic electron configuration is [Ar] 4s² 3d⁷.

The Co²⁺ ion has a 2+ charge so has lost two electrons. These electrons are lost from the 4s orbital before the 3d. Remember that '4s are gained first and lost first'!

The correct answer is therefore [Ar] 4s⁰ 3d⁷.

Each and every orbital can hold two electrons. Any s sub-level contains one orbital and can therefore hold two electrons. Any p sub-level contains three orbitals and can therefore hold six electrons. Any d sub-level contains five orbitals and can therefore hold ten electrons. Any f sub-level contains seven orbitals and can therefore hold fourteen electrons.

The n=4 energy level consists of the 4s, 4p, 4d and 4f sub-levels.

Thus the answer is 32 (2+6+10+14).

Orbitals are plots of electron position (90% probability) around the nucleus. They are three dimensional (not planar). An s-orbital is a sphere; a p-orbital is a three dimensional figure-of-eight.

So the answer here that best decribes as s-orbital is .

The red figure-of-eight image represents a p-orbital.

For HL students only: The elongated blue image represents a sigma molecular orbital (two orbitals overlapping end on) and the elongated red image represents a pi molecular orbital (two p-orbitals overlapping side on).

The sub-levels of an atom are filled in the following order: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s. Remember that 's' sub-levels hold a maximum of 2 electrons, 'p' hold 6, and 'd' hold 10.

A copper atom has 29 electrons in total (atomic number is 29), but the configuration is not what would be expected as the electrons in the 4s and 3d energy levels are 4s¹ 3d¹⁰ instead of filling the sub-levels in the conventional manner (4s² 3d⁹). Chromium and copper have unusual configurations and need to be learned.

Remember that [Ar] is shorthand and indicates the electron configuration of argon: 1s²2s²2p⁶3s²3p⁶.

The correct answer is therefore 1s² 2s²2p⁶3s²3p⁶4s¹3d¹⁰

The upper number is the mass number, which is equal to protons plus neutrons. The lower number is the atomic number which is the number of protons. The number of electrons is equal to the number of protons in a neutral atom, but this is 2+ positive ion, so it has two fewer electrons than protons.

So the species has 20 protons, (44−20) 24 neutrons and 18 electrons (two fewer than protons).

The line absorption spectrum of hydrogen is composed of discrete lines that represent particular frequencies. Lines are produced by electron transitions from lower to higher energy levels (for absorption; from higher to lower for emission).

The lines converge at higher frequencies/energies which corresponds to lower wavelengths.

Any lines in the absorption spectrum are not seen as coloured lines, but as black lines (an absence of colour) as electromagnetic radiation is absorbed (not emitted).

Thus the answer is 2 only.

The upper number on the left is the mass number, which is equal to protons plus neutrons. The atomic number for zinc is 30 and for copper is 29; this is the number of protons, shown on the periodic table.

The number of electrons is equal to the number of protons in a neutral atom, but these species are positive ions so will have more protons than electrons.

⁶⁵Zn²⁺ therefore has 30 protons, 65−30=35 neutrons, and 30−2=28 electrons (as it is a 2+ ion).

⁶⁵Cu⁺ therefore has 29 protons, 65−29=36 neutrons, and 29−1=28 electrons (as it is a 1+ ion).

The correct answer is therefore Both have the same number of electrons.

The upper (superscript) number on the left is the mass number, which is equal to protons plus neutrons. The atomic number, which is the number of protons is shown on the periodic table. The number of electrons is equal to the number of protons in a neutral atom but negative ions will have correspondingly more electrons and positive ions correspondingly fewer.

⁸Li⁺ has 8−3=5 neutrons and 3−1=2 electrons

⁸Li has 8−3=5 neutrons and 3 electrons

³¹P³⁻ has 31−15=16 neutrons and 15+3=18 electrons

³¹P has 31−15=16 neutrons and 15 electrons

¹⁵N³⁻ has 15−7=8 neutrons and 7+3=10 electrons

¹⁵N has 15−7=8 neutrons and 7 electrons

The correct answer is therefore ⁸Li⁺, ³¹P, ¹⁵N as this is the only set in which all species contain more neutrons than electrons.

Longer wavelength corresponds to lower frequency/lower energy. So the longest wavelength will correspond to the electron transition of lowest energy.

The question also asks about emission - energy given out - so the transition must be from a higher to lower energy level.

The energy gaps between the levels get smaller at higher energy.

Therefore the smallest energy transition that is also an emission is n=6 to n=5, which is therefore the correct answer.

The electron configuration reflects an element's position on the periodic table.

The easiest way to solve this is to count the total number of electrons (23); as this is an atom, the number of electrons will be equal to the number of protons, so the element is vanadium.

Vanadium is in Group 5, Period 4.

The upper number is the mass number, which is equal to protons plus neutrons (19 sub-atomic particles in the nucleus). The lower number is the atomic number which is the number of protons. The number of electrons is equal to the number of protons in a neutral atom, but this is a 1− negative ion, so it has one more electron than protons.

So this fluoride ion has 9 protons, (19−9=)10 neutrons and 10 electrons (1s² 2s² 2p⁶).

The question states that there is only one stable isotope of fluorine so all stable fluoride ions will have 10 neutrons.

The correct answer is therefore The ion has the same electron configuration as an atom of argon as this is incorrect: Argon has an electron configuration of 1s² 2s² 2p⁶ 3s² 3p⁶.

The upper number on the left is the mass number, which is equal to protons plus neutrons. The atomic number for krypton is 36, which is the number of protons; shown on the periodic table.

⁸²Kr therefore has 36 protons and (82−36=)46 neutrons.

The correct answer is therefore 36 protons, 46 neutrons.

The sub-levels of an atom are filled in the following order: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s.

Remember that 's' sub-levels hold a maximum of 2 electrons, 'p' hold 6, and 'd' hold 10, and that [Ar] is shorthand and indicates the electron configuration of argon: 1s²2s²2p⁶3s²3p⁶.

A vanadium atom has 23 electrons in total (atomic number is 23) so the condensed atomic electron configuration is [Ar] 4s² 3d³.

The V³⁺ ion has a 3+ charge so has lost three electrons. These electrons are lost from the 4s orbital before the 3d. Remember that '4s are gained first and lost first'! So two electrons are lost from 4s and one electron is lost from 3d.

The correct answer is therefore [Ar] 4s⁰ 3d².

Each and every orbital can hold two electrons. Any s sub-level contains one orbital and can therefore hold two electrons. Any p sub-level contains three orbitals and can therefore hold six electrons. Any d sub-level contains five orbitals and can therefore hold ten electrons. Any f sub-level contains seven orbitals and can therefore hold fourteen electrons.

The n=3 energy level consists of the 3s, 3p, and 3d sub-levels.

Thus the answer is 18 (2+6+10).