Unit 2: The Atom

what is an atom?

what is an atom?

the smallest unit of matter

what is an atom made of?

protons, neutrons, electrons

what are the characteristics of a proton

positive charge, in the nucleus, has mass, and identifies the element

what are the characteristics of a neutron

neutral charge, in the nucleus, has mass, and stabilizes the nucleus

what are the characteristic of an electron

negative charge, in the shells of the atom, no relative mass, and involved in bonding

what is average atomic mass

the weighted average of all the different isotopes of an element - unit: amu

how do you find the # of neutrons in an atom?

rounded atomic mass - protons = neutrons

what is an isotope

atoms of the same element with different numbers of neutrons

what does mass number represent

the number of protons and neutrons in an atom

what are ions

atoms that gain or lose electrons when becoming charged particles

what is a cation

atom loses electrons and it becomes positively charged. ex: Na^+

what is an anion

a gain in electrons which makes it negatively charged. ex: Cl^-

how do you know what version of an element is most abundant?

the one closest to the average mass

what is a half-life

the time required for a substance to decay by half (t1/2)

which is consistent in half-life decay: the percent decrease or the number decrease?

percent - b/c the number changes

what are the 3 types of decay

alpha, beta, gamma

why do elements go through these 3 types of decay?

to become more stable

what is the symbol for alpha

fish looking thing

what is the symbol for beta

B with tail

what is the symbol for gamma

loopy y

what charge does alpha have?

positive

what charge does beta have?

negative

what charge does gamma have?

no charge

is alpha, beta, or gamma the biggest?

alpha

what elements primarily use alpha decay?

element numbers 83+

what happens to the atom when it goes through alpha decay?

It releases protons and neutrons. The mass decreases by 4 (top), and the atomic number decreases by 2 (bottom)

what element is associated with alpha?

helium (He)

what happens to the atom when it goes through beta decay?

the isotope releases an electron and the atomic number increases by 1

are protons or electrons associated with beta?

electrons

what happens to the atom when it goes through gamma decay?

an isotope releases gamma rays. nothing changes about the atom but it moves to a stable energy level

what is penetrating power

how easily each type of radiation can pass through different materials

do smaller or larger atoms have higher penetrating power?

smaller (easier to pass through a substance)

what is ionizing power

the ability of radiation to damage molecules

do larger or smaller particles cause more damage to the substance they enter?

large

what is fission

the breaking apart of atoms

what is fusion

the combination of 2 atoms

what is the nickname for the atomic bomb

fission bomb

what is the nickname for the hydrogen bomb

thermonuclear bomb

what elements are involved with the reactions of the bombs?

U (uranium) and Pu (plutonium)

is the atomic bomb or hydrogen bomb stronger?

hydrogen

how is fission involved in the hydrogen bomb?

it creates the conditions for fusion to occur

what is carbon dating?

using the known rate of decay to date a fossil using carbon

what version of carbon is used in carbon dating

carbon-14

would an older fossil have more or less carbon?

less

democritus

- found matter is made of small, indivisible particles called atoms.

-model: solid sphere

john dalton

- elements are made of unbreakable particles called atoms (wrong)

-atoms of the same element are identical in every way (wrong)

-atoms combine in simple whole number ratios to form compounds

-chemical reaction involves rearrangement of atoms, not a complete change

dmitri mendeleev

-created the periodic table in 1869

-discovered a pattern in elements

jj thomson

-discovered the first subatomic particle: electron

-the electron is negatively charged

-performed the cathode ray tube experiment

-model: plum pudding

Cathode Ray Tube Experiment

he put a magnet on the vacuum tube and saw that it was attracted to the positive side meaning that it was negatively charged

ernest rutherford

-discovered that all positive charge is located in a tiny, dense core: the nucleus

-did the Gold Foil Experiment

- nuclear model (first one with a nucleus)

Gold Foil Experiment

shot alpha particles at thin gold foil, most went straight through showing that there it is mostly open space, and some deflected meaning there was a small, dense, positive charge in the core

niels bohr

-planetary model

-electrons orbit the nucleus and everything has its place - they can jump between but always on one

erin schrodinger

-quantum model

-found that electrons exist in shells/clouds of various shapes called orbitals

james chadwick

-discovered the neutron is in the nucleus and that it has no charge

what is Avogadro´s number

6.022×10²³

what is molar mass

the mass of 1 mol of a substance

what is the symbol (unit) for molar mass

g/mol

where do you find what the molar mass of an atom is?

its atomic mass