Bonding and structure

Question 1

Ionic bond

Answer 1

strong electrostatic forces between oppositely charged ions

Question 2

what do ionic compounds form

Answer 2

giant ionic lattice structure

Question 3

properties of ionic compounds
(giant ionic lattices) and why

Answer 3

-high melting and boiling points
-conduct electricity only when molten or dissolved
-soluble in water (ions make attractions to the h+ and o- atoms in the water molecules)

Question 4

which factors affect the strength of ionic bonds

Answer 4

-ionic charge (stronger when bigger)
-ionic radius (stronger when smaller)

Question 5

lone pairs

Answer 5

any pair of electrons that are not bonding

Question 6

covalent bonding

Answer 6

a strong electrostatic force of attraction between a shared pair of electrons and the nuclei of two bonded atoms

Question 7

dative covalent bond

Answer 7

covalent bond in which both electrons in the shared pair come from one atom

Question 8

what groups are the lone pair donors

Answer 8

5,6,7

Question 9

what groups have vacant orbitals

Answer 9

2,3

Question 10

what 2 possible type of structures can atoms that bond covalently form

Answer 10

simple molecular and giant covalent

Question 11

how is a dative covalent bond represented

Answer 11

its an arrow coming from the lone pair to the vacant orbital

Question 12

how do u deal with a negative charge when drawing dot and cross diagrams

Answer 12

use a third symbol (star or square) to show that the electron has come from another species

Question 13

what is the shape of a 3d molecule given by

Answer 13

the arrangement of electron pairs (bonding and lone) around the central atom

Question 14

give the number of bonding regions, lone pairs and the arrangement and angle of a linear molecule

Answer 14

-2
-0
-all atoms are in a straight line
-180 degrees

Question 15

give the number of bonding regions, lone pairs and the arrangement and angle of a trigonal planar molecule

Answer 15

-3
-0
-all atoms are arranged as a flat triangle around the central atom
-120 degrees

Question 16

give the number of bonding regions, lone pairs and the arrangement and angle of a tetrahedral molecule

Answer 16

-4
-0
-four atoms arranged evenly around the central atom forming a 3d shape
-109.5 degrees

Question 17

give the number of bonding regions, lone pairs and the arrangement and angle of a trigonal pyramid molecule

Answer 17

-3
-1
-Three atoms around a central atom forming a pyramid like 3d shape
-107 degrees

Question 18

give the number of bonding regions, lone pairs and the arrangement and angle of a non-linear molecule

Answer 18

-2
-2
-two atoms around the central atom that are not in a straight line
-104.5 degrees

Question 19

give the number of bonding regions, lone pairs and the arrangement and angle of a octahedral molecule

Answer 19

-6
-0
-six atoms arranged evenly around a central atom in 3D
-90 degrees

Question 20

how to explain shapes with only bonding regions

Answer 20

there are x bonding regions which repel as far apart as possible (they are evenly spaced)

Question 21

how to explain shapes which involve lone pairs

Answer 21

there are x bonding regions and y lone pairs, lone pairs always repel more than bonding pairs

Question 22

electronegativity

Answer 22

the ability of an atom to attract the electrons in a covalent bond

Question 23

what are the two trend in electronegativity

Answer 23

as group number increases it also increases as period number increases it decreases (this excludes group 8)

Question 24

what are the most electronegative atoms

Answer 24

F2, O2 and Cl2

Question 25

what factors affect the electonegativity of an atom

Answer 25

-nuclear charge/number of protons (more=higher) -size of atom (bigger=lower) -shielding (more=lower)

Question 26

what is a non-polar covalent bond

Answer 26

if a covalent bond is of atoms with the same element or with very similar electronegativity (within 0.5 of each other) the electrons are shared equally and the covalent bond is described as non-polar

Question 27

polar bonds

Answer 27

when there is a difference in electronegativity of 0.5 or more between two bonded atoms and the electrons are shared unequally (an asymmetrical molecule with an overall dipole)

Question 28

charges in polar bonds (not the same as formal charges seen on an ion )

Answer 28

The more electronegative atom pulls electrons more and gets a partial negative charge where as the less electronegative atom pulls electrons less and gets a partial positive charge

Question 29

whats a dipole

Answer 29

the separation of charge in a polar bond (a non polar bond has no dipoles)

Question 30

how can a molecule contain polar bonds but be a non polar molecule

Answer 30

If a molecule has polar bonds but is symmetrical the dipoles will cancel each other out and it will become non polar

Question 31

how do u spot if a molecule is symmetrical

Answer 31

-if there are only bonding pairs (no lone pairs) on the central atom AND all atoms surrounding the central atom are the same

Question 32

how do u spot if a molecule is unsymmetrical

Answer 32

if any atom surrounding the central atom is different to others OR if theres any lone pairs on the central atom

Question 33

intermolecular forces

Answer 33

occur in simple molecular substances; they are forces between molecules. they vary in strength but are relatively weak compared to ionic and covalent bonds

Question 34

what are the types of intermolecular forces from weakest to strongest

Answer 34

-london forces -permanent dipole-dipole forces -hydrogen bonding

Question 35

london forces

Answer 35

its between ALL molecules

Question 36

permanent dipole-dipole forces

Answer 36

only between POLAR molecules, this is in addition to london forces

Question 37

hydrogen bonding

Answer 37

only if the molecules contain N-H, O-H or F-H bonds this is only in addition to london forces

Question 38

whats special about N O and F

Answer 38

they are the most electronegative atoms and have atleast 1 lone pair

Question 39

how do london forces arise

Answer 39

-in every molecule electrons are moving constantly, this can make one side of a molecule slightly negative and the other slightly positive which forms a TEMPORARY DIPOLE, this dipole causes a dipole to form in a neighbouring molecule. this is called an induced dipole. the attraction between the partial positive charge in one molecule and the partial negative charge in another is known as london force

Question 40

factors that affect the strength of london forces

Answer 40

1. Number of electrons- the more electrons there are in a molecule the higher the chance of temporary dipoles forming which makes london forces between the molecules stronger 2. Surface area contact- the more the surface area contact= the more london forces between molecules

Question 41

how do permanent dipole-dipole forces arise

Answer 41

they can occur between polar molecules only, polar molecules have a permanent dipole, there is an attraction between the partial positive side of one molecule and the partial negative side of a neighbouring molecule which is known as the permanent dipole-dipole force

Question 42

hydrogen bonding explained:

Answer 42

it happens because O N and F are the most electronegative atoms and they have a lone pair. there is a big difference in electronegativity between the H and the O or N or F so their bond has a large dipole. a hydrogen bond is the attraction between the lone pair on O N or F and the partial positive charge on the hydrogen

Question 43

anomalous properties of water

Answer 43

solid water (ice) is less dense than liquid water meaning there are less particles on water as a solid than a liquid this is because water can form 2 hydrogen bonds per molecule because O is very electronegative and it has 2 lone pairs. the hydrogen bonds hold the water molecules further apart in ice than in liquid water.

Question 44

physical properties of simple molecular structures

Answer 44

-Low melting points and boiling points → because molecules are held together by weak intermolecular forces -Often gases or liquids at room temperature → weak forces don’t need much energy to overcome. -Do not conduct electricity → no free ions or delocalised electrons -Solubility depends on polarity: Non-polar molecules dissolve in non-polar solvents polar molecules dissolve in polar solvents (like water)