Unit 2: Chemistry - Atoms and Elements

Question 1

Atom

Answer 1

Smallest piece of matter
Mostly made of empty space
Made of 3 sub atomic particles (protons (+), neutrons (o), electrons (-)

Question 2

Molecule

Answer 2

Any combination of two more more atoms that are chemically “bonded” together

Question 3

Element

Answer 3

Pure substance made of all the same atom(s)
Can be solid, liquid, gas
ex. gold

Question 4

Compound

Answer 4

Substance made of molecules from two or more different atoms/elements bonded together
ex. water = compound, 3 atoms (not an element)
insulin = compound, more than 500 atoms
*coumpounds vary in size and is not a mix substance + compounds have multiple molecules

Question 5

Substance

Answer 5

Compostition always same, but different atoms –> different melting + boiling points

Question 6

Pure vs. Mix Substances

Answer 6

Pure Substance:
Made of same atoms or has same ratio
ex. water = pure –> 2 hydrogen : 1 oxygen
Mix Substance:
Mix of atoms that are not bonded together but share same space

Question 7

Do an element’s properties transfer to the properties of a compound?

Answer 7

No
ex. Hydrogen = gas at room temp, odorless, explodes near flame, lightest gas
Oxygen = gas at room temp, odorless, needs fire to burn
2 Hydrogen : 1 Oxygen = Water
Water = liquid at room temp, odorless, colorless, tasteless, *puts out fires

Question 8

What is sodium, chlorine, and sodium chloride?

Answer 8

Sodium (Na) = solid at room temp, soft, shiny metal, highly reactive
Chlorine (Cl) = gas at room temp, yellowish green, very poisonous, heavy gas
Sodium Chloride “table salt” (NaCl) = solid at room temp, white crystals, tastes good, not poisonous, dissolves in water
*Properties do not transfer when making compound

Question 9

What is a “fixed ratio?”

Answer 9

Ratios between elements are always the same for that compound

Question 10

Why are compounds different?

Answer 10

Same elements but have different ratios between atoms = makes compound different
All elements + compounds are made up of different types of atoms –> different properties like melting + boiling points + different states of matter at room temp

Wh

Question 11

Why is the periodic table shaped the way it is?

Answer 11

Organized in collumms based on the elements’ properties

Question 12

Who is Mendeleev?

Answer 12

Did not create the periodic table
Did not arrange elements
Figured how to identify unknown elements’ properties based on elements around them

Question 13

Electrons

Answer 13

(-) charge
- attracted to protons (+) and neutrons (o)
- stays within orbit because of protons and neutrons
- circles around nucleus

Question 14

Protons

Answer 14

(+) charge
- aka atomic number of element
ex. atomic number: 3, protons: 3
- # of protons = ~neutrons = ~ electrons
- forms nucleus
- attracted to neutrons
- never changes
- # unique for each element

Question 15

Neutrons

Answer 15

(o) charge
- acts as glue for protons and electrons
- forms nucleus
*99.9% of mass of element = atoms

Question 16

Shells

Answer 16

• or energy levels/orbits
• where electrons are
• # of shells is same as row on Periodic Table
• < 2 for first row
• < 8 for second row
• < 18 for third row

Question 17

How do you find the atomic mass and number?

Answer 17

Atomic number = number of protons
Atomic mass = the number of protons and neutrons
ex. number of protons = 12
Atomic mass = 12 + 12 = 24