Gr.11 Isotopes, Trends, & Atomic Theory

Question 1

What is an Isotope?

Answer 1

Same element atoms - same # of protons, different # of neutrons

Question 2

What is the unit for isotopes

Answer 2

u - unit ot amu - atomic mass unit

Question 3

How do you find abundance

Answer 3

• Get the avg mass of the element on periodic table
• iso¹(x) + iso²(1-x)
• sub iso² into the brackets
• put x with x’s on one side
• solve for x
• x × 100 -> = abundance minus 100 for y abund
  OR y = 1 - 0.00 (x) (y=1-x)

Question 4

How do you find avg atomic mass

Answer 4

(Mass of iso¹ × abundance¹/100) + (Mass iso² × abundance²/100) = avg atomic mass

Question 5

What are the 5 sorts of trends of the periodic table?

Answer 5

Atomic radius, ionization energy, electron affinity, electronegativity, and the shielding effect

Question 6

What is atomic radius?

Answer 6

It is the distance from nucleus to nucleus with 2 atoms’ valence shell touching each other.

Question 7

What is atomic radius measured in?

Answer 7

Picometers (pm)

Question 8

What happens to atomic radius when moving left to right and why

Answer 8

It decreases. Electrons and protons are added 1 by 1 to the same shell and can’t shield each other from being attracted to their opposite. This makes nuclear charge (protons basically) go up which decreases atomic radius

Question 9

What happens to atomic radius when moving up to down and why

Answer 9

It increases. Increasing electrons means increasing shells and electrons further away from the nucleus. Just think radius; by design it sort of makes sense. bigger circle = bigger radius

Question 10

What is ionization energy?

Answer 10

The energy required to remove the 1st valence electron from a neutral atom. The closer the electron is to the nucleus the more energy is required for it to be removed

Question 11

What is ionization energy measured in

Answer 11

KJ/mole (kilojoule)

Question 12

What happens to ionization energy when moving left to right and why

Answer 12

Increase. This is because atomic radius decreases, which means the valence is closer to the nucleus and more strongly drawn in

Question 13

What happens to ionization energy when moving up-and-down and why

Answer 13

Decrease. Because the atomic radius increases, so valence becomes further away so the nucleus has less of a pull

Question 14

Why does group I have low ionization energy?

Answer 14

Because when an electron is lost it forms a stable octet, so the hold on the valence isn’t so strong. They all want to be stable all the time.

Question 15

What is electron affinity?

Answer 15

It is the ability of an atom to accept an electron, and the energy absorbed or released in the process.

Question 16

Which family has the lowest electron affinity and why

Answer 16

Alkaline earth metals. You’d think it’s Group I, but they’re quick to lose an electron and become positive, which attracts electrons. Group II isn’t as quick to do that, so they attract the least electrons

Question 17

What is electronegativity?

Answer 17

It is the measure of attraction of an atom to the electrons in a chemical bond. Closely related to ionization energy.

Question 18

What happens to electronegativity when moving from up to down

Answer 18

It decreases. Atomic radius increases making electrons further from the nucleus and the nuclear charge decreases as well

Question 19

What happens to electronegativity when moving left to right and why

Answer 19

It increases. Atomic radius decreases and nuclear charge increases, attracting more electrons to itself

Question 20

What is effective nuclear charge and what should you know about it

Answer 20

The attractive positive charge of nuclear protons acting on valence electrons
- The effective nuclear charges is always less than total # of protons present in nucleus due to the shielding effect
- Effective nuclear charge is behind all other periodic table tendencies

Question 21

What is the shielding effect charge and what should you know about it

Answer 21

The lessening of attraction between nuclear protons and valence electrons by partially or fully filled inner shells

• Shielding effect increases with the number of inner shells of electrons
• Same shell electrons do not shield each other

Question 22

Who are the 6 forefathers of atomic theory

Answer 22

Democritus, John Dalton, J.J. Thomson, Ernest Rutherford, Niels Bohr, and Erwin Schrödinger

Question 23

What was Democritus’ time and contributions

Answer 23

400 BC, Greece
- started the search for a description of matter
- theorized matter would become indivisible at some point, the point which he named “atomos” - not to be cut
- atoms are infinite, always moving, and can join together

Question 24

Why was Democritus ignored

Answer 24

Outshone by the more eminent philosophers of that time - Aristotle and Plato

Question 25

What was Dalton’s time and contributions

Answer 25

Early 1800’s, England
- his experiments lead to the acceptance of the idea of atoms
- this recognition is known under “Dalton’s Law”, a pillar of modern chemistry; which includes the following:
• all elements are made up of atoms
• atoms are indivisible and indestructible
• same elements are alike, differents are different
• compounds formed by the joining of two atoms

Question 26

What was Thomson’s time and contributions?

Answer 26

1897, England
- plum pudding model, the first hint that an atom had even smaller particles in it
- concluded that negative charges came from within the atom
- that meant there was particles smaller than an atom
- which made the atom divisible!
- old electrons were called corpuscules
- he figured positive charges existed too since the gas was neutral, but he couldn’t find them

Question 27

Describe the experiment that guided Thomson to finding that atoms are divisible

Answer 27

In an experiment involving a neutral gas tube and an electric current: from the current, a negative charge came through, so a particle smaller than the atom had to exist - where else would they have come from?

Question 28

What is the Plum Pudding model and who created it

Answer 28

J.J. Thomson. It said that atoms were made of a positively charged substance scattered with negative electrons, like raisins in plum pudding

Question 29

What was Rutherford’s time and contributions

Answer 29

1908, England
- made a popular atomic model
- Conducted the gold foil experiment which lead to the discovery of the nucleus (coined that name too)
- all pos charges were inside the nucleus, neg charges were scattered outside the nucleus around the edge
- the atom is mostly empty space
- father of nuclear physics

Question 30

Describe the gold foil experiment and who conducted it

Answer 30

Ernest Rutherford.
He send positively charged bullets through gold foil. Some bullets went straight, others went awry and different places as if it hit a solid. Knowing pos repels pos, he concluded that the center of the atoms had a condensed, positively charged nucleus!

Question 31

What was Niels Bohr’s time and contributions

Answer 31

1913, Denmark
- proposed an improvement to Rutherford’s model which assigned electrons to a specific energy level
- it was the first successful model of the atom
○ it was made with thoughts of relating atoms to the solar system, electrons orbiting the nucleus
○ and, the orbital energy levels were located at certain distances

Question 32

What is the wave model?

Answer 32

Modern Day Chemistry
- disproved Bohr’s idea of orbitals and location of electrons
- based off the principles of wave mechanics
- concluded that it is impossible to determine exact location of an electron
- probable location is based on energy amount of the electron

Question 33

Describe the modern atomic model

Answer 33

A positively charged nucleus surrounded by enough electrons to make a neutral atom

Question 34

What is an electron cloud

Answer 34

The space where electrons are likely to be found. Electrons do not move randomly, probable location may depend on the amount of energy the electron has
Low energy: closest to nucleus
High energy: furthest from nucleus

Question 35

What is Erwin Schrödinger’s time and contributions

Answer 35

1935, Austrian-Irish
- considered a founder of quantum mechanics
- best known for Schrödinger’s Cat and Schrödinger’s Equation
-