Atom structure and bonding
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62 Terms
What are the three subatomic particles in an atom?
Protons, neutrons and electrons.
What charge does a proton have?
+1 (positive).
What charge does a neutron have?
0 (neutral).
What charge does an electron have?
-1 (negative).
Where are protons and neutrons found?
In the nucleus.
Where are electrons found?
In orbitals surrounding the nucleus.
What is the atomic number (Z)?
The number of protons in an atom.
What is the mass number (A)?
The total number of protons and neutrons.
How do you calculate the number of neutrons in an atom?
Neutrons = mass number (A) - atomic number (Z).
How many electrons does a neutral atom have?
The same number as protons.
What are isotopes?
Atoms of the same element with the same number of protons but different numbers of neutrons.
What determines the identity of an element?
Its atomic number.
What is isotopic notation?
A way of showing an element's mass number and atomic number, e.g. ¹²₆C.
How many protons, neutrons and electrons are in carbon-12?
6 protons, 6 neutrons and 6 electrons.
How many protons and neutrons are in fluorine-18?
9 protons and 9 neutrons.
How many electrons are present in a neutral atom of fluorine-18?
9 electrons.
How many electrons are present in F⁻?
10 electrons.
What is an atomic orbital?
A region of space where there is a high probability of finding an electron.
What is a shell?
A collection of orbitals with the same principal quantum number (n).
What are the four main types of orbitals?
s, p, d and f.
What is the shape of an s orbital?
Spherical.
What is the shape of a p orbital?
Dumbbell-shaped.
How many electrons can occupy a single orbital?
Two electrons.
How many electrons can the first shell hold?
2 electrons.
How many electrons can the second shell hold?
8 electrons.
What is the ground-state electron configuration?
The lowest-energy and most stable arrangement of electrons in an atom.
What is the Aufbau principle?
Electrons fill the lowest-energy orbitals first.
What order do orbitals fill according to the Aufbau principle?
1s → 2s → 2p → 3s → 3p → 4s → 3d.
What is the Pauli exclusion principle?
No two electrons in an atom can have the same set of four quantum numbers; an orbital can hold a maximum of two electrons with opposite spins.
What is Hund's rule?
Electrons occupy orbitals of equal energy singly before pairing, with parallel spins.
What is the electron configuration of hydrogen?
1s¹.
What is the electron configuration of carbon?
1s² 2s² 2p².
What is the electron configuration of sodium?
1s² 2s² 2p⁶ 3s¹.
What is the electron configuration of fluorine?
1s² 2s² 2p⁵.
What are valence electrons?
Electrons in the outermost shell of an atom.
Why are valence electrons important?
They determine bonding and common ion charges.
Why do atoms form bonds?
To achieve a lower-energy, more stable electron arrangement.
What is the octet rule?
Atoms gain, lose or share electrons to achieve eight electrons in their outer shell.
What charge do Group 1 elements commonly form?
+1 cations.
Why do Group 1 elements form +1 ions?
They lose one valence electron to achieve a noble gas configuration.
What charge do halogens (Group 7) commonly form?
-1 anions.
Why do halogens form -1 ions?
They gain one electron to complete their outer shell.
What is an ion?
A charged atom formed by gaining or losing electrons.
What is a cation?
A positively charged ion formed by loss of electrons.
What is an anion?
A negatively charged ion formed by gain of electrons.
What is ionic bonding?
The electrostatic attraction between oppositely charged ions formed by electron transfer.
What happens to electrons during ionic bonding?
They are transferred from one atom to another.
What is a pharmaceutical example of an ionic compound?
Metformin hydrochloride.
What is covalent bonding?
A bond formed when atoms share pairs of electrons.
What happens to electrons during covalent bonding?
They are shared between atoms.
What types of elements usually form covalent bonds?
Non-metals.
What is a Lewis structure?
A diagram showing valence electrons as dots and bonds as shared electron pairs.
What is a bonding pair?
A pair of electrons shared between two atoms in a covalent bond.
What is a lone pair?
A pair of valence electrons not involved in bonding.
How many bonds does hydrogen usually form?
One bond.
How many bonds does carbon usually form?
Four bonds.
How many bonds does nitrogen usually form?
Three bonds.
How many bonds does oxygen usually form?
Two bonds.
How many lone pairs are typically found on nitrogen in ammonia (NH₃)?
One lone pair.
How many lone pairs are typically found on oxygen in water (H₂O)?
Two lone pairs.
Why are lone pairs important?
They affect molecular shape, reactivity and interactions with biological targets.
Why are isotopes important in pharmacy?
Radioactive isotopes such as fluorine-18 and technetium-99m are used in diagnostic imaging.