Unit 1 half test

Question 1

How the history of an atom evolved

Answer 1

1) Greek democritus had the idea for an atom: NO protons No electrons, No neutrons

2) John Dalton: Billiard balls no P no E no N

3) J.J thomson: Plum pudding model. Random negative spots everythign was positive.

4) Ruthorford: Centre was positive (neucleus) with elections

4.5/5) Bhor: Same thing with energy levels (shells)

6) Chadwick: added neutrons

7) Schrodinger: electron cloud

Question 2

What is the law of constant composition

Answer 2

Compounds always have the same percentage composition by mass. (Same formula)

Question 3

What are isotopes

Answer 3

Two atoms are isotopes if they have the same number of protons, but they have different numbers of neutrons.
This means that:
Isotopes are atoms of the same element.
Isotopes have different atomic masses.
Isotopes have different number of neutrons in their nuclei.

Question 4

In the average atomic mass equation
(AAM (u) = (% ab1 x mass1) + (% ab2 x mass2) +… )
What does AAM mean, %ab mean, and mass mean.

Answer 4

AAM = Average Atomic Mass
%ab1 = Percent abundance of isotope
mass1 = Mass of isotope

Question 5

What is periodic law

Answer 5

When elements are arranged in order of increasing atomic number, there is a regular pattern in their chemical and physical properties – i.e. periodic trends

Question 6

What do elements in the same group share

Answer 6

the same outer orbital configuration in consecutively higher energy levels

Question 7

What do elements in the same period share

Answer 7

outer electrons in the same energy level

Question 8

What is atomic radius, what factors affect it, and what is the trend

Answer 8

The distance between the nucleus and the valence electrons

1)Number of shells

2)Strengths of attractions felt by the valence electrons toward the nucleus (Nuclear Charge)(Zeff)

3)Shielding effect

The trend:
arrow pointing bottom left

Question 9

What is the Nuclear charge

Answer 9

of electrons also increases, but inner layers are still the same 🡪 nuclear (proton) pull is stronger

Ignore that its glitched^

.
A measure of the stregth of a nucles’ pull as we move across a period the number of protons increases in nuclear charge.
This affects periodic trends

Question 10

What is the sheilding effect

Answer 10

electrons in innermost shells “block” or shield the outermost electrons from the nucleus’ attractive force.

This mainly effects group trends.

Question 11

Trends in ionic radius

Answer 11

Positive ions are smaller than the neutral atoms from which they are formed
Electrons are lost from energy levels farthest from the nucleus
Fewer electrons but same “+” pull from nucleus 🡪Remaining electrons pulled closer to the nucleus
Negative ions are larger than the neutral atoms from which they are formed
Electrons are gained, resulting in smaller effective nuclear charge for the greater number of electrons
Repulsive forces between electrons increases across the periods

Question 12

What is ionization energy, what factors affect it, and what is the trend

Answer 12

The amount of energy required to remove an electron from an atom or ion in the gaseous state. Outer electrons are easier to remove

1)Strengths of attractions felt by the valence electrons toward the nucleus (Nuclear Charge)(Zeff)

2)Shielding effect

arrow pointing top right

Question 13

What is electron affinity

Answer 13

Electron Affinity – A measure of the energy lost or gained when an electron is added to an uncharged atom.

The lower the number, the greater the electron affinity.

Greater E.A. means that energy is actually released when an electron is added. Therefore, the value is expressed as a negative. Units for both i.e. and e.a. are KJ/mol.

Eg. X + 1e- = X- + energy
The greater the attraction between an atom and an added electron the more energy that will be released.

Arrow pointing top right

Question 14

What is electronegativity

Answer 14

Electronegativity is a measure of an atom’s ability to attract shared electrons to itself.

You have the trend for this on your periodic table.

Arrow pointing top right

Question 15

What does isoelectronic or the octet rule mean

Answer 15

“Atoms tend to bond in such a way that will allow them to have 8 electrons in their valence shells.”

(Hydrogen and Helium are obvious exceptions since they only need 2 electrons to fill their outer shell)

Question 16

What type of bond forms large crystal lattice structures

Answer 16

Ionic compounds (and some covalent compounds like diamond)

Question 17

What is a combining capacity

Answer 17

The combining capacity is the number of covalent bonds that a non-metal atom will usually make to form a stable molecule.
Recall the ball & peg molecules that you made earlier. The number of holes in each type of atom represents its combining capacity.

Question 18

what is ammonia

Answer 18

NH3

Question 19

What are the tresholds for ionic, polar, and nonpolar bonds.

Answer 19

ΔEN > 1.7, Then the bond is ionic.
1.7 - 0.5 , Then the bond is polar covalent.
0.1 - 0.4, Then the bond is non polar 0, then the bond is pure covalent.

Question 20

What molecular shape does 2 total, 2 bonds and 0 lone pairs have

Answer 20

linear 180*

Question 21

What molecular shape does 3 total, 2 bonds and 1 lone pairs have

Answer 21

Bent 120*

Question 22

What molecular shape does 3 total, 3 bonds and 0 lone pairs have

Answer 22

trigonal planar
120*

Question 23

What molecular shape does 4 total, 4 bonds and 0 lone pairs have

Answer 23

tetrahedral 109.5*
(triangle based piramid)

Question 24

What molecular shape does 4 total, 3 bonds and 1 lone pairs have

Answer 24

Trigonal pyramidal 107*
(triangle based piramid with no top)

Question 25

What molecular shape does 4 total, 2 bonds and 2 lone pairs have

Answer 25

bent 104.5*
water

Question 26

when is a molecule polar

Answer 26

A molecule is said to be polar if it contains polar covalent bonds AND its shape is “asymmetrical”

Question 27

What are london dispersion forces or Van der Waals’ forces

Answer 27

This force of attraction is caused by the random creation of temporary dipoles within molecules known as “instantaneous dipole moments”.

Consider that electrons are always in motion. Thus, even in a non-polar molecule there will be instances when the movement of electrons results in partially positive and partially negative regions which attract neighbouring molecules. This occurs randomly, but frequently.

The strength of dispersion forces increases as the molecular mass of the molecule increases due to an increase in the number of electrons allowing for the creation of stronger instantaneous dipoles. Thus, large molecules often have higher boiling points.

Question 28

What are dipole-dipole attractions

Answer 28

Electrostatic attraction which occurs between molecules with permanent dipoles, ie. polar molecules.
This permanent dipole means that the molecules ‘stick’ together
this means they require energy to pull apart ergo a higher m.p/b.p
tend not to be gasses at room temperature

Eg. HCl

Question 29

What is hydrogen bonding

Answer 29

Electrostatic attraction which occurs between molecules with permanent dipoles, ie. polar molecules.
This permanent dipole means that the molecules ‘stick’ together
this means they require energy to pull apart ergo a higher m.p/b.p
tend not to be gasses at room temperature

fluorine, oxygen, or nitrogen.

Question 30

what is an intramolecular force

Answer 30

Recall that intramolecular forces hold atoms together within a molecule. Such bonds determine the chemical properties of a compound such as reactivity.

(One molecule)

Question 31

what are intermolecular forces

Answer 31

Intermolecular forces exist between molecules, and influence physical properties.

(many molecules)