Chapter 2 - Atoms, Molecules, and Ions

Question 1

Who is Empedodes?

Answer 1

A philosopher from (492-432BC) who thought about the concept of “elements”.

Question 2

What were some of Empedodes’ thoughts about the concept of elements?

Answer 2

• There are 4 elements: Fire, air, water, and earth.
• Matter exists in specific variations of these
• The problem is that they cannot break down into fundamental elements.

Question 3

Who is Democritus?

Answer 3

He is the one that first thought about the atomic viewpoint of Matter.

Question 4

What were some of Democritus’ ideas?

Answer 4

• divide matter until infinitesimally small and no longer dividable.
• Atomos-indivisible

Question 5

What did Aristotle believe about all of the atomic theories?

Answer 5

Aristotle believed there was no indivisible unit

- he set back atomic theory for ~2000 years

Question 6

Who was John Dalton?

Answer 6

He came up with a theory that was based on the four postulates.

Question 7

What was John Dalton’s Theory? (The four postulates)

Answer 7

An element is composed of tiny, indivisible particles called atoms

• All atoms of a given element are identical and have identical properties
• Atoms of different elements combine (in whole number ratios) to form compounds.
  
  • Different whole number ratios yield different compounds
  • Law of Definite proportions
• Atoms cannot be created or destroyed (by chemical reaction)
  - Law of conservation of mass

Question 8

What did J.J. Thomson and Robert Milliken discover?

Answer 8

They “discovered” and characterized the electron by the use of cathode rays. Cathode rays formed from a voltage applied across negative/positive electrodes can be manipulated by electric or magnetic fields.

Question 9

Rutheford discovered…?

Answer 9

Through alpha particle scattering, it showed that the nucleus is dense and concentrated in a small volume at the core of an atom. Most of the atomic volume is empty space explored by electrons.

Question 10

What are Atoms made up of?

Answer 10

Subatomic particles Electrons, Protons, and neutrons

Question 11

What charge and mass does an electron have?

Answer 11

Negatively charged with tiny mass, orbiting around the nucleus

Question 12

What charge and mass does a proton have?

Answer 12

Positively charged and part of the nucleus

Question 13

What charge and mass does a neutron have?

Answer 13

Neutral charge and part of nucleus

Question 14

What makes up most of the the atomic mass?

Answer 14

Protons and Neutrons

Question 15

Why do atoms have a neutral charge?

Answer 15

Because they have a equal number of protons and electrons

Question 16

What are AMUs?

Answer 16

Atomic mass units

Question 17

What does 1 AMU equal?

Answer 17

1.66054 x 10^-24

Question 18

What is the atomic mass unit of a proton?

Answer 18

1.0073 AMU

Question 19

What is the atomic mass unit of a neutron?

Answer 19

1.0087 AMU

Question 20

What is the atomic mass unit of an electron?

Answer 20

5.486 x 10^-4 AMU

Question 21

What is an angstrom? What does 1 angstrom equal?

Answer 21

It is a non-SI unit of length used for atomic dimensions. 1 Angstrom = 1 x 10^-10 m.

Question 22

What are isotopes?

Answer 22

Isotopes are atoms of a given element that can differ in the number of neutrons. Ex. Carbon-12, Carbon-13, Carbon-14

Question 23

How do you find the mass number of a certain atom?

Answer 23

Mass number = protons + neutrons

Question 24

What does the atomic number of a atom tell us?

Answer 24

it tells us the number of protons a certain element has (and electrons since atoms are neutral)

Question 25

How do you determine the Atomic weight of an element?

Answer 25

By finding the average atomic mass of an element, using masses of its isotopes and their relative abundances. (The atomic weight is what is reported on the periodic table)

Question 26

What is the equation to find the atomic weight?

Answer 26

Atomic weight = Sigma (isotope mass x fractional abundance)

Question 27

What are the rows of the periodic table called?

Answer 27

periods; atomic number increases by 1 every element across a period (protons and electrons do too)

Question 28

What do the columns of the periodic table determine?

Answer 28

it determines the “groups”

Question 29

What do the elements in a particular group have in common.

Answer 29

They tend to have the same chemical properties or behavior.

Question 30

What is group 1 called?

Answer 30

alkali metals

Question 31

What is group 2 called?

Answer 31

Alkaline earth metals

Question 32

What is group 17 called?

Answer 32

halogens

Question 33

What is group 18 called?

Answer 33

noble gases

Question 34

What is a molecular formula?

Answer 34

A molecular formula indicates total number of atoms in a molecule
Ex: CO2: 1 carbon atom, two oxygen atoms

Question 35

What is an empirical formula?

Answer 35

Chemical formulas that give only the relative number of atoms of each type in a molecule.
Ex: Molecule: C6H12O6 Empirical: CH2O

Question 36

How are Ions formed?

Answer 36

When electrons are removed from or added to an atom, the charged particle is called an ion.

Question 37

What is a cation?

Answer 37

A cation is an atom that has LOST electrons to become POSITIVELY CHARGED

Question 38

What is an Anion?

Answer 38

An anion is an atom that has GAINED electrons to become NEGATIVELY CHARGED.

Question 39

How does the periodic table help to predict the most stable ion of a particular element?

Answer 39

By looking at how many groups over they are to the nearest gas. (check figure 2.20 in text book)
Ex: Na is a 1+, Cl is a 1-, Group 2 elements are 2+ etc.

Question 40

What are Ionic compounds?

Answer 40

When two atoms or molecules come together with mutually beneficial electron needs
Ex: Na + Cl —- Na+Cl-

Question 41

Make sure to know how to predict chemical formulas for ionic compounds.

Answer 41

Look at periodic table and determine “desired charge” for ions in the compound. Practice balancing formulas to end up with neutral charge for compound.