Units 1 & 2 TEST

9/17 B DAY, 9/18 A DAY - Significant Figures & Scientific Notation, Atomic History & Structure, Light & Energy, Periodic Table & Trends, Lewis Dot & Electron Configuration

How many Significant Figures are in the number 100.25?

five

How many Significant Figures are in the number 0.00340 ?

three

Round 45730.2 to three significant figures.

45700

Round 0.0035071 to two significant figures.

0.0035

What is 450,000 in scientific notation?

4.5 × 10⁵

What is 0.000321 in scientific notation?

3.21 × 10^-4

What charge do protons have and where are they located?

positively-charged, located in the nucleus

What charge do neutrons have and where are they located?

neutral (no charge), located in the nucleus

What charge do electrons have and where are they located?

negative charge, located outside the nucleus in the cloud. “orbits” nucleus.

What does the atomic number tell us?

the number of protons an element has

How do you find mass number?

protons + neutrons = mass number

How do you calculate average atomic mass?

Avg. Atomic Mass = (mass 1 x abundance 1) + (mass 2 x abundance 2) + …

repeat for however many isotopes there are. remember to convert your abundances to decimals before calculating (divide by 100 or move decimal two spaces to the left)

What were the four postulates of Dalton’s Atomic Theory?

1. all matter is made up of atoms

2. atoms of an element are identical in size, mass, and other properties; atoms of different elements differ in size, mass, and other properties.

3. Atoms of different elements combine in simple whole-number ratios to form chemical compounds.

4. In chemical reactions, atoms are combined, separated, or rearranged.

What is the relationship between wavelength and frequency and energy?

An inverse relationship

long-wavelength = low frequency = low energy

short-wavelength = high frequency = high energy

What is the order of the electromagnetic spectrum from longest to shortest wavelength?

radio, microwave, infrared, visible, UV, x-ray, gamma

What is the order of the visible light spectrum from longest to shortest wavelength?

red, orange, yellow, green, blue, indigo, violet

the rainbow - ROY G BIV

What experiment did Rutherford conduct and what did he discover?

Gold Foil Experiment

discovered the positively-charged nucleus

What experiment did J.J. Thompson conduct and what did he discover?

Cathode Ray Tube Experiment

discovered electrons

Which atomic model did John Dalton create?

the Solid Sphere Model

thought atoms were indivisible

Which atomic model did J.J Thompson create?

the Plum Pudding Model

looks like a chocolate chip cookie - positively charged dough, negatively charged chips/plums

Which atomic model did Rutherford create?

the Nuclear Model

Which atomic model did Bohr create?

the Planetary Model

electrons orbit the nucleus like the planets orbit the sun in our solar system

Which atomic model did Schrödinger and Heisenberg create?

the Quantum (Cloud) Model

discovered electrons do not orbit the nucleus in fixed paths, but rather in clouds or probability called “orbitals”

On the periodic table, vertical columns are known as…

groups

On the periodic table, horizontal rows are known as…

periods

What is the name for the elements in group 1A and what properties do they have?

Alkali metals

most reactive metals, soft, silvery color

What is the name for the elements in group 2A and what properties do they have?

alkaline earth metals

harder and stronger than alkali metals, not as reactive but still very reactive

What is the name for the elements in group 7A and what properties do they have?

Halogens

most reactive nonmetals, gases

What is the name for the elements in group 8A and what properties do they have?

Noble gases

very stable, extremely unreactive

All the elements to the left of the stair-step line (except hydrogen) are …

metals

All the elements to the right of the stair-step line are …

nonmetals

All the elements on the stair-step line are called…

metalloids

What is the order of the sublevels when writing electron configurations?

1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s…

What is the electron configuration for oxygen (O)?

1s²2s²2p⁴

What is the electron configuration for selenium (Se)?

1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁴

What is the Lewis Dot structure for Silicon?

four individual dots on each side of silicon’s symbol, Si

What is the Lewis Dot structure for oxygen?

two pairs of electrons and two lone electrons around oxygen’s symbol, O

What is electronegativity?

the ability for an atom to attract electrons

low electronegativity = bad at attracting electrons

high electronegativity = good at attracting electrons

What is ionization energy?

the amount of energy needed to remove an electron from an atom

low IE = easily loses electrons

high IE = easily gains electrons

What is atomic radius?

the size of an atom

What is the trend for electronegativity on the periodic table?

increases up and to the right

What is the trend for ionization energy on the periodic table?

the same as electronegativity

increases up and to the right

What is the trend for atomic radius on the periodic table?

opposite of electronegativity and ionization energy

increases down and to the left

Why does atomic radius increase as you go down the periodic table?

there are more energy levels, so the atom gets bigger