Chemical Bonding and Structure

Question 1

what is a lattice?

Answer 1

repeating, 3D pattern of atoms arranged in a regular order

Question 2

what is a chemical bond?

Answer 2

described as the force that causes a group of atoms to behave as a unit

Question 3

what are bonds the result of?

Answer 3

Bonds result from the tendency of a system to seek its lowest possible energy and hence are more stable.

Question 4

what is an ionic bond?

Answer 4

Bond between oppositely-charged ions (very different electronegativities).

Question 5

what is a metallic bond?

Answer 5

a bond formed between metals (low electronegativity) due to the electrostatic attraction between a lattice of positive ions and delocalized electrons

Question 6

what is a covalent bond?

Answer 6

a bond formed between nonmentals (high electronegativity)

Question 7

when elements react they can? (ionic)

Answer 7

transfer electrons and form ionic bonds: between a positive ion (usually a metal) and a negative ion to achieve an octet or noble gas configuration

Question 8

when elements react they can? (covalent)

Answer 8

share electrons and form covalent bonds usually between 2 nonmetals to achieve an octet

Question 9

Ionic compound formula?

Answer 9

the ionic compound is the simplest ratio of the elements in an ionic lattice (known as formula units)

Question 10

what is isoelectronic?

Answer 10

having the same number or structure of electron, isoelectronic ions are different elements that have identical electronic configurations

Question 11

what is lattice enthalpy?

Answer 11

the energy required to break 1 mole of an ionic bond into its ions in the gaseous state (higher enthalpy = greater energy required to break)

Question 12

what is ionic radii?

Answer 12

the distance from the nucleus of an ion to the outermost shell of its electrons, the smaller the radii, the greater the attraction therefore the stronger the ionic bond

Question 13

what is electrostatic attraction?

Answer 13

The attraction between protons and electrons

Question 14

why does ionic compounds have high mp and bps?

Answer 14

because of the strong attractive electrostatic forces holding the oppositely charged ions together and a large number of ionic bonds in the crystal lattice. These require a lot of thermal energy to overcome and hence have both high melting and boiling points.

Question 15

volatility

Answer 15

tendency of a substance to change into a gas

Question 16

volatility in ionic compounds

Answer 16

ionic compounds tend to have low volatility due to a strong electrostatic attraction between the oppositely charged ions.

Question 17

are ionic soluble?

Answer 17

yes, many ionic substances are soluble in water.

Question 18

are ionic compounds conductors?

Answer 18

as solid, ionic compounds do not conduct electricity since they do not have mobile ions, but in a liquid (molten) state ionic compounds conduct electricity since they have mobile ions.

Question 19

brittleness in a lattice

Answer 19

when a lattice is hit a layer of its ions shifts so that ions of the same charges line up, these like charges repel each other causing the lattice to shatter.

Question 20

why do we get a sea of delocalized electrons in metals?

Answer 20

metals are more stable without their valence electrons and tend to lose them, therefore their valence electrons are not very strongly held by the nucleus and they form positively charged ions resulting in the sea of delocalized e

Question 21

about metallic bonds

Answer 21

occurs between metallic atoms
does not result in the formation of a compound, but hold metal atoms together in a three dimensional arrangement known as a close-packed lattice

Question 22

Why do metals conduct electricity?

Answer 22

Metals conduct electricity because their delocalized electrons can move freely and carry an electric current.

Question 23

How do impurities affect electrical conductivity in metals?

Answer 23

Impurities in a metal resist the movement of electrons, increasing electrical resistance. This is why high purity copper is essential in electrical wiring

Question 24

Why do metals conduct heat

Answer 24

Metals conduct heat because delocalized electrons can easily carry vibrations (heat energy) through the metal

Question 25

Define temperature

Answer 25

Temperature is a measure of the average kinetic energy of a substance

Question 26

Define kinetic energy

Answer 26

Kinetic energy is the energy due to motion

Question 27

How is heat transferred

Answer 27

Heat is transferred by the transfer of kinetic energy.

Question 28

What does malleable mean?

Answer 28

Malleable means a metal can be pounded or hammered into sheets or other shapes without breaking.

Question 29

Why are metals malleable

Answer 29

Metals are malleable because their positive ions can slide past each other while maintaining attraction to the "sea" of delocalized electrons. The metallic bond is not rigid and is non-directional

Question 30

What factors influence the strength of a metallic bond

Answer 30

The strength of the bond (and thus melting and boiling points) depends on: Charge Density of the Cations: Higher charge density leads to stronger bonds. Number of Delocalized Electrons: More delocalized electrons contribute to stronger bonds. Radius of the Metal Cation: Smaller radius leads to stronger bonds due to closer proximity of electrons and nucleus.

Question 31

What is the state of metals at room temperature?

Answer 31

All metals are solids at room temperature EXCEPT FOR MERCURY (Hg)! Mercury is a silver liquid at room temperature. They are solids because they have strong electrostatic attraction between the ions and the delocalized electrons.

Question 32

Why do metals have high melting and boiling points

Answer 32

Metals have a high melting point and boiling point because they have strong electrostatic attraction between the positive ions and the delocalized electrons

Question 33

What is the trend for melting and boiling points across a period (for metals)

Answer 33

m.p. and b.p. increase across a period (for metals) as the number of valence electrons increase, it increases the number of delocalized electrons, and thus is also an increase in the number of protons (ENC increase). Number of energy levels stays the same. The attraction between positively-charged ions and the delocalized electrons increases. Increasing the strength of the bond and hence the m.p. and b.p.

Question 34

What is the trend for melting and boiling points down a group (for metals)

Answer 34

m.p. and b.p. decrease down a group (for metals). The ENC stays the same. The number of energy levels increase. The attraction between positively charged ions and the delocalized electrons decreases. Decreasing the strength of the bond and hence the m.p. and b.p.

Question 35

Are metals volatile? Why or why not?

Answer 35

Metals are not volatile. They do not turn into a vapor at a low temperature because of the strong electrostatic attraction between the positively-charged ions and the delocalized electrons.