Chem Test: Atomic Structure and Periodic Table

Law of conservation of mass

Law of conservation of mass

The mass of the reactants must be equal to the mass of the products in a chemical reaction

Law of definite proportions

A chemical compound always contains the same elements with the same proportions by mass in every state of matter

Law of multiple proportions

When the same 2 elements form 1+ compound, the masses of the elements form a small whole number ratio

John Dalton's atomic theory

All matter is composed of extremely small particles called atoms. Atoms of the same element are identical in terms of size, mass, and other properties. Atoms of one element are different from the atoms of any other element. Atoms of different elements can chemically combine with one another in simple whole-number ratios to form chemical compounds. Chemical reactions can be described as the separation, combination, or rearrangement of atoms. Atoms of one element cannot be changed into atoms of a different element as a result of a chemical reaction.

contribution of Dalton to atomic theory

Created his 4 points of atomic theory using the 3 laws above, used the scientific method and experiments to prove his work

Contribution of Ernest Rutherford to atomic theory

Used sheets of gold foil and positively charged alpha particles to prove that atoms had a lot of empty space

contribution of JJ Thompson to atomic theory

Used cathode ray tubes to prove that electrons were negatively charged particles present in all atoms, developed a plum pudding model of positive and negative charges

Thompson plum pudding model

accounts for the negative particles in atoms while reconciling the neutral charge of an atom

Cathode Ray Tube Experiment

All atoms must have electrons Positive charge somewhere

Gold Foil Experiment (Rutherford)

Directed stream of alpha particles at sheet of foil Majority of particles get deflected and did not penetrate the foil (contrary to what plum pudding model argued)

Conclusions of Gold Foil Experiment

Plum pudding model is incorrect Most atomic mass is in nucleus Atom is mostly empty space Electrons move around the nucleus

Hydrogen Atomic Emissions Model (Bohr)

Planetary model of atomic structure: electrons travel around the nucleus in circular orbits Loses energy as it orbits the nucleus Gains energy thru photons Electrons do not collapse into oppositely charged nucleus due to fixed energy levels When electrons fall/jump from level to level they emit/require QUANTUM of energy

Quanta/Quantums of Energy

the unit an electron moves when energized, like rungs of a ladder electrons can't be in-between energy levels

structure of the nuclear atom

Nucleus: small, dense, central core of the atom Protons- positively charge Neutrons- neutral charge

Protons

Positively charged particles

Neutrons

neutrally charged particles

Electrons

Negatively charged particles

Atomic number

the number of protons in the nucleus of an atom

Mass Number

protons+neutrons

Atomic Mass

average number of protons and neutrons in a nucleus according to the percentage of naturally occurring isotopes

Isotopes

atoms with the same atomic number that have different numbers of neutrons

the relationships between speed, wavelength, and frequency of light

Inversely proportional Wavelength increases = frequency decreases Speed of light = wavelength * frequency

Photoelectric Effect

The emission of electrons from a metal when light shines on the metal, showed light is made of atoms (photons)

Waves/duality of light

Behaves as both particles and waves Ex radio waves

Duality of Light

light is both a particle and a wave

What scientists thought before? (light)

Frequency is the number of cycles per second on the wave length, while intensity or amplitude is how much energy a wave has (true). They thought that intensity would affect the speed of electrons displaced (since the energy would be transferred and energy depends on intensity). They thought frequency would impact the number of electrons ejected since more cycles can collide with the electrons

What actually happened? (frequency, Intensity) what did Einstein realize about light?

frequency only affected speed while intensity only affected numbers. Intensity had no effect on the speed/energy of the electrons. This made Einstein realize light was not only a wave: they were made up of small particles called photons.

differences between atoms due to their differences in occupied principal energy level (shells) by electrons

Those with full shells are very stable, and those with not-full shells are unstable and looking for electrons

Periods (periodic table)

horizontal lines (rows)

Groups (periodic table)

vertical lines (columns)

Metals

1st and 2nd groups, easiest for them to lose electrons

Nonmetals

noble gases and other elements that are a gas

Metalloids

all the elements on the steps of the periodic table

Atomic Radius (trend in a period)

As the atomic number increases in a period, the atomic radius decreases

Atomic Radius (trend in a group)

as you go down a group the size increases because of the shielding effect

Electronegativety

Increases from left to right in a period, based off of ability to attract shared electrons

Ionization energy

Energy needed to remove an electron from an atom, increases from left to right in a period

relationship between group number and valence electrons

Group number = # of valence electrons

Cation

(loses electrons to create full shells) Overall smaller because neutral atoms now have more P+ than e- Nucleus pulls electrons in closer

Anion

(gains electrons to become negative) Overall bigger because there are more e- than P+ and nucleus can't hold onto electrons