Chemistry Final Exam .

Why does a tennis ball have more volume than a golf ball?

takes up more space

physical properties

a quality or condition of a substance that can be observed or measured without changing the substance’s composition

Heterogeneous mixture

not uniform throughout

homogeneous

evenly disrupted and uniform NOT EASILY DISTINGUISHED

mixture

physical blend

substance

uniform and definite

chemical properties

flammable, combustable, ability to rust

chemical change

a change that produces matter with a different composition

C₁₂H₂₂O₁₁

12 carbon, 22 hydrogen, 11 oxygen.

how would you identify 2 elements with similar properties?

same group

Daltons improvement over Democritus:

atoms keep their identity in a chemical change

JJ Thomson’s improvement on Dalton’s theory:

atoms contain tiny, negatively charged electrons

True model of atom

Electrons around the nucleus, occupy almost all the volume of the volume atom

NOT true:

atoms of isotopes of an element have different numbers of p+

All atoms are:

neutral w/ the # of p+ equaling the # of e-

TRUE:

atoms of isotopes of an element have different numbers of neutrons

If E is the symbol for an element, which two represent isotopes of the same element?

20/10 E, 21/10 E, NOT 20/11 E, 21/9 E

How many p+ and e- if atomic number is 50 and the mass number is 125?

50 p+, 50e-, and 75 neutrons

why do Dalton’s ideas constitute a theory while Democritus do not?

Dalton’s ideas were experimented/tested on (experimental evidence), while Democritus’ ideas were not

What Rutherford observation hypothesized that atoms are mainly empty space, and contain a dense center?

Gold foil experiment; empty space —> particles right through; dense center —> particles deflected backwards

Dalton’s theory to explain law of conservation of mass

Part 4 of Dalton’s theory

Example of matter

steam coming off a pot

observation

obtain info

hypothesis

proposed explanation

scientific law

a short statement that SUMMARIZES the results of many observations and experiments

theory

well tested explanation for a broad set of observations

Independent variable

you change, manipulated variable

dependent variable

observed, responding variable

experiment

test a hypothesis

scientific method

a logical and systematic approach to the solution of a scientific problem

control

comparison

compare and contrast theories + laws

a hypothesis a proposed explanation for an observation, a theory well tested explanation for a broad set of observations. Hypotheses and theories are similar by both being explanations for observations.

Compare contrast theories + law

Theories and laws are similar because both are experimented and observed, theories and laws are different because theories are explanations but laws are statements.

hypothesis can become a _____ after tested

theory

Modern periodic table

arranged in order of increasing atomic number

Who arranged elements by atomic mass and used the arrangement to predict properties of elements?

Dimitri Mendeleev

Each period (in the periodic table) corresponds to an

energy level

Majority of elements are

metals

Poor conductor

nonmetal

shielding effect remains constant by

elements have same number of core e-

electronegativity

ionization energy

decreases w increasing atomic number in group 2A

ionization energy

as you move left to right across a period

ionization energy increases

True (about ions)

anions form when an atom gains e-

C[He] 2s²2p² what is the highest number of v.e- in the highest occupied energy level

4 v.e-

Selenium

(Se[Ar]3d¹⁰4s²4p⁴)

Why does it take less energy to remove an electron from a barium atom than a calcium atom?

ionization energy decreases down a group, while S.E. increases

Why does fluorine have a greater ability to attract e- than Boron does?

electronegativity increases across a period, while N.P. also increases

is boron atom (B) or boron ion (B³⁺) larger?

Boron atom bc boron ion loses 3 while the atom stays the same

How to tell what period an element is in? how do you know?

The energy level determines the period (highest occupied energy level) position on the periodic table

how to tell what group elements are in? how do you know?

The number of valence electrons determines an element’s group position

Noble gas configuration for Arsenic (As)

[Ar]3d¹⁰4s²4p³

[He]2s² what is the group and period?

group: 2A

period:2

3s²3p⁵

period 3, group 7A

they have similar physical and chemical properties cesium, rubidium, potassium, lithium bc they

are in the same group (1A) bc of their # v.e.-

Nicks Bohr’s contribution to development of atomic structure

electrons travel in circular orbits around the nucleus

Quantum mechanical model of the atom

concerned with probability of finding an e- in certain positions

atomic orbitals in 3rd energy level

s,p, and d only

Max number of - in d orbital

10

number of d orbitals in any energy level

5

Aufbau principle

electrons enter orbitals of lowest energy first

e- moves from lower to higher energy level, e-…

absorbs a quantum of energy

Emission of light from an atom occurs when a e-

drops from a higher to a lower energy level

atomic emission spectra of a sodium atom on earth and the sun…

would be the same

Know what 6s²

6- energy level, s- atomic orbital, 2- number of e-

What happens when new experiment evidence cannot be explained by the existing theory or model, describe an example from chap 4 or chap 5 to support answer/

The theory is changed completely or modified.

ground state e- config for aluminium

1s²2s²2⁶3s²3p¹

Compare and contrast planetary model to Bohr

Both: nucleus (with p+/n), specific paths, orbit (e-)

Bohr: energy levels

Compare and contrast Bohr model and quantum mechanical model

bohr: orbit, specific path

Both: Nucleus, energy levels

Quantum: e- cloud, likely location —> atomic orbital

pauli exclusion principle

an atomic orbital may describe at most two electrons

Hunds rule

if electrons have room to spread out they will

500,000 scientific notation

5.0 × 10⁵

0.000,000,042

4.2 x 10^-8

0.000,837

8.37 × 10^-4

(3.0×10^-3)x(2.5×10^-4)=

7.5 × 10^-7

(9.4×10^-2)-(2.1×10^-2)

7.3×10^-2

5.00 sig fig

3

22 meter sticks sig fig

0

0.074 sig fig

2

40.007 sig fig

5

divison and multiplication

round to sig figs