Chapter 3 - Atomic Combinations

Question 1

What is a covalent bond?

Answer 1

A covalent bond is a chemical bond between two non-metals were valence electrons are shared between their orbitals.

Question 2

What is an ionic bond?

Answer 2

An ionic bond is a chemical bond between a metal and a non-metal where electrons are transferred between each other

Question 3

What is a metallic bond?

Answer 3

A metallic bond is a chemical bond between two metals

Question 4

What is the difference between a molecule and a compound?

Answer 4

A molecule is two or more atoms, of the same element, that are chemically bonded together.

A compound is a type of molecule where two or more atoms are chemically bonded together, however, the atoms are of more than one element

Question 5

What do electrons of an atom always try to do when bonding with another atom?

Answer 5

Electrons always try to occupy the lowest possible energy level.

Question 6

Explain the graph regarding the relationship between the distance between the nuclei of two hydrogen atoms and the energy level of the system.

Answer 6

As the two hydrogen atoms are brought close together, the energy of the system decreases and the prevalence interaction is attraction. This leads to a negative potential energy and eventually they reach a distance between their nuclei where the energy of the system reaches a minimum. This is when the attractive and repulsive forces are equal. As they get closer, the repulsive force grows stronger than the attractive forces and the energy of the system increases.

Question 7

What is a lone pair?

Answer 7

A lone pair is a pair of electrons that occupy an orbital in an atom or molecule, but are directly involved in bonding and affect the molecular configuration when bonded to other atoms

Question 8

What is a dative or co-ordinate covalent bond and how can it be formed?

Answer 8

A dative or co-ordinate covalent bond is a covalent bond where the electrons shared between two atoms comes from the same atom.

It can be formed when an atom with a lone pair is bonded with an atom with no electrons (ion)

Question 9

Why is molecular shape important?

Answer 9

Molecular shape is important in determining how molecules interact and reacts with other molecules and how the boiling and melting points are affected.

Question 10

What is the VSEPR theory and what is it based on?

Answer 10

VSEPR stands for Valence She’ll Electron Pair Repulsion. The VSEPR theory states that valence electron pairs in a molecule will arrange themselves in a configuration where the repulsive forces between the negative charges are at a minimum. In other words, as far as possible from each other. It is based on the idea that the topology of a molecule is determined by the repulsion force between pairs of electrons around a central atom

Question 11

Draw the different molecular shapes

Answer 11

Mark out of 7

Question 12

What is the relationship between a bent/angular molecular configuration and the tetrahedral molecular shape?

Answer 12

The bent/angular molecular shape has the same electron geometry as the tetrahedral molecular shape, but a different molecular geometry

Question 13

What are ideal shapes and name the 5 ideal shapes?

Answer 13

Ideal shapes are symmetrical molecular configurations with no lone pairs. These are linear, trigonal planar, tetrahedral, trigonal bypyramidal, and octahedral.

Question 14

What is the configuration/molecular shape of all diatomic compounds and give a few examples?

Answer 14

Linear. E.g. Hydrogen gas, Sodium Chloride, oxygen gas, hydrochloric acid

Question 15

What is a chemical bond?

Answer 15

A chemical bond is a physical process that causes atoms to become attracted to each other

Question 16

What is electronegativity?

Answer 16

Electronegativity is the tendency of an atom in a molecule to attract a shared pair of electrons

Question 17

What factors affect electronegativity and how?

Answer 17

The number of protons (atomic number) an atom has and it’s atomic radius are the two factors that affect electronegativity.

No. of protons: Protons are positively charged and attract particles with unlike charges or electrons. Ergo, the more protons an atom has, the higher it’s electronegativity.

Atomic radius: Protons in the nucleus and electrons in the orbitals are attracted to each other as they are unlike charges, therefore, as they grow apart from one another, the attraction decreases and, therefore, the electronegativity decreases.

Question 18

What are the electronegativity trends in the periodic table?

Answer 18

Electronegativity increases across a period and decreases down a group. Over the whole periodic table, an arrow can be drawn from the bottom left to the top right as the trend line.

Question 19

How can electronegativity be used in bonding?

Answer 19

Electronegativity between two atoms can be used to determine the type of bond that exists between them

Question 20

Give the values of the difference in electronegativity between two atoms and the type of bond they correlate with

Answer 20

0: non-polar covalent
0-1: weak polar covalent
1.1 - 2.1: strong polar covalent
>2.1: Ionic bond

Question 21

Why don’t the difference in electronegativity between two atoms form a metallic bond?

Answer 21

Metals have a low electronegativity and, therefore, electrons are not drawn strongly to any one atom

Question 22

What is polarity?

Answer 22

Polarity is the separation of electric charges leading to a molecule having an electric dipole moment with a negatively charged end and a positively charged end.

Question 23

Why is polarity important?

Answer 23

The polarity of a molecule is important as it affects properties such as solubility and the melting and boiling points

Question 24

What is a dipole?

Answer 24

A dipole is when one side of a bond has a greater electron density than the other

Question 25

What is a partial charge?

Answer 25

A partial charge is the slightly positive or slightly negative charge of an atom in a polar covalent bond

Question 26

How are partial charges represented?

Answer 26

Partial charges are represented by lowercase delta positive or lowercase delta negative

Question 27

How to determine whether a compound is polar or non-polar

Answer 27

1. Draw the Lewis diagram and determine the molecular configuration
2. Determine whether the bonds are polar or not
   3a. If the dipoles are symmetrical, then it is non- polar
   3b. If the dipole are asymmetrical, then it is polar

Question 28

What is bond length?

Answer 28

Bond length is the distance between the nuclei of two atoms when they bond

Question 29

What is bond energy?

Answer 29

Bond energy is the amount of energy that must be added to the system to break the bond that has formed

Question 30

What is bond strength?

Answer 30

Bond strength is how strongly an atom is attracted to and held by another

Question 31

What is bond strength dependent on and how is it affected by these factors?

Answer 31

Bond strength is dependent on the size of atoms bonded, the bond length and the number of bonds between the atoms.

• The shorter the bond length, the greater the bond strength
• The smaller then atom sizes when bonding, the greater the bond strength
• The more bonds that exist between atoms, the greater the bond strength

Question 32

Out of this whole chapter, how well do you understand and know it?

Answer 32

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