Unit #1 test review 🌟

What is ordinary matter made from?

Made from the atoms from the 92 elements.

What are atoms made of?

Smaller particles: protons, neutrons, electrons.

What did Dalton discover?

1. "Atoms cannot be created or destroyed, only rearranged through chemical reactions."
2. All elements are made from atoms.
3. Compounds are made from combining atoms in whole # ratios.

What charge do electrons have?

Negative, -.

Do atoms have a charge?

No, most are neutral.

Are the # of protons and electrons equal in a neutral atom?

Yes.

True/False: The number of protons determines the element.

True! (ex. Hydrogen H has 1, Tin Sn has 50)

How do atoms interact with each other?

Via their electrons.

Is the nucleus the center of the atom? And what is it made of?

Yes! Made from neutrons and protons.

What was Democritus' model of the atom?

A hard sphere.

What was Democritus' main idea?

Matter is made of very small and invisible particles, "atomos."

What was Dalton's model and thinking? And was was cool about it?

Same thinking as Democritus! Matter was made up of atoms. Model = hard sphere

What did JJ Thomson discover and HOW?

The electron! Through cathode ray experiments.

What was JJ Thomson's model of an atom?

Plum-pudding model. The + must exist to cancel the -, in order to create neutral atom. NO NUCLEUS IN THIS MODEL!

Who did the gold foil/alpha scattering experiment?

Rutherford!

What did the gold foil/alpha scattering experiment show?

1. There is a nucleus in the atom and it is positively charged (because sometimes the alpha particle would shoot back, instead of going through. It would hit the nucleus = the nucleus has a very big impact).
2. The atom is mostly empty space (most of the alpha particles went straight through the gold foil without any problem).

What was Rutherford's model of the atom?

Tiny, dense, and positively charged nucleus. Light, negative electrons surrounding it.

What did Rutherford discover?

All atoms have most of their mass concentrated in a tiny, dense, and positively charged nucleus.

What is the atomic number of an element? And where is it on the periodic square?

The # of protons in the nucleus. Located TOP right in the square: it determines the element. (ex. Zinc's atomic number is 30).

Do all the atoms of the same element have the same # of protons?

Yes. All Helium atoms = 2 protons, Carbon atoms = 6 protons.

How does the nucleus stay together?

Neutrons and protons (+) repel each other.

True/False: Atoms of the same element won't necessarily have the same # of neutrons.

True!

What is this number represent: (Carbon-12, Carbon-13)

The # of neutrons.

Atomic mass

The weighted average mass of all isotopes of an ELEMENT, (amu = units).

What process is when atomic nucleus decays or gives off energy?

Radioactivity.

What is the lightest particle in the nucleus?

The electron- they are very very fast!

In reality, what is the electron cloud the size of?

An atom!

How is electromagnetic force LIKE and UNLIKE gravity?

LIKE: acts of electric charge
UNLIKE: electromagnetic force can attract/repel

What are ions?

Charged atoms. They have an uneven # of protons to electrons.

Difference between Na & Na^1+

Na = 11 protons, 11 electrons
Na^1+ = 11 protons, 10 electrons.

True/False: if an atom has over 97 protons, it is radioactive.

Sort of! It must have OVER 83 PROTONS.

What is a chemical reaction?

Creates new compounds (something that is >2 elements) FROM elements.

What is a nuclear reaction?

Creates new elements FROM other elements. 2 MAIN TYPES.

2 types of nuclear reactions.

1. Decay reactions (nucleus spontnsly. breaks up).
2. Bombardment reactions (nucleus is struck by another nucleus/proton/neutron).

What is radiation?

Transmission of matter, energy, waves through space. CAN BE DANGEROUS when it has high energy (breaks chem. bonds in molecules).

Atomic mass equation.

(mass of iso. #1)x(abundance of iso. #1 in DECIMAL FORM) + (however many isotopes you have).

Atomic # vs Atomic mass.

(Atomic weight is the same thing as atomic #).

Alpha decay.

- Unstable nucleus shoots out 2 PROTONS + 2 NEUTRONS = to
create new daughter nucleus.
- 42He is the alpha particle that is shoots out.

How do the # of protons/neutrons, atomic # and mass # change when ALPHA decay?

Protons: -2
Neutrons: -2
Atomic #: -2
Mass #: -4

Beta decay.

when unstable nucleus emits electron (0-1e)

How does the atomic # and mass # change after beta decay?

Atomic #: +1
Mass #: No change.

Gamma decay.

When an excited nucleus decreases its energy by emitting HIGH ENERGY electromagnetic radiation.

Write the equation for the gamma decay of Cobalt-60.

60,27Co -> 0,0 γ + 60,27Co

How do the protons/neutrons, atomic #/mass # change after going through gamma decay?

ALL STAY THE SAME!

What is a positron?

(0,+1e). A nuclear particle (has the same mass as an electron), but ➕ charge

Positron emission.

When the nucleus releases a proton into 1. a positron, 2. a neutron. Neutron stays inside nucleus.

How do the protons/neutrons and atomic#/ mass# change after positron emission?

Protons: -1
Neutrons: +1
Atomic #: -2
Mass #: STAYS SAME

Equation for positron emission.

What is half-life?

The time that it takes for half a sample to decay.

Equation for half life.

What do you put into a table to find half-life?

# of half lives
time (units)
amount remaining (units)

What is radioactive dating?

using the half-life of a radioactive isotope to determine how old something is. LOOKING BACK.

What is nuclear fission?

The forced splitting of a nucleus.

What are some real-world scenarios of nuclear fission?

Atomic bombs.
Nuclear power-plants (control rods keep it under control).

What is light? What is its range?

Form of electromagnetic energy, mainly comes from electrons in atoms. Range goes from radio-waves (LOW energy) to gamma rays (HIGH energy).

True/false: Wavelength (λ) and frequency (ν) are DIRECTLY related.

FALSE. They are INVERSELY related.

Units of wavelength (λ)?

Meter (m).

Unit of frequency (v)?

Hertz or 1/s (s^-1).

What is the speed of light? And what is the symbol for it?

3.0 x 10^8 m/s, c

What is the equation for speed?

c = λv

Units of energy (E)?

Joules.

Equation for energy?

E = hv

What is Planck's constant?

h = 6.626 x 10^-34

What is a photon?

Quantum of light.

How is energy quantized?

Looks like a staircase. Jumps of energy are made SO SMALL that energy seems continuous.

What is Bohr's model of the atom?

- Electrons are in ORBIT around the nucleus @ specific distances with specific amounts of energy
- Each electron has a "ground state"/normal.
- Electrons jump UP to higher state (absorb energy). Higher state = "excited state".
- Electron jumps DOWN to "normal state", releases energy in form of LIGHT.

What is the atomic emission spectrum?

specific spectral lines, indicate SPECIFIC wavelengths of light released from an atom. UNIQUE TO EVERY ELEMENT

Penetration & mass of alpha decay.

- Alpha particles can be shielded by paper +skin. LEAST harmful.
- MOST mass (8,000x of beta): 4 amu.

Penetration & mass of beta decay.

- Beta particles shielded by aluminum. INTERMEDIATE harmful.
- INTERMEDIATE mass: 1,200 amu

Penetration & mass of gamma decay.

- Gamma decay shielded by 2inch lead. MOST harmful.
- 0 mass (it's energy).