Chem EX 1

No two electrons can have the same four quantum numbers is known as the

Pauli exclusion principle

Only two electrons, with opposing spins, are allowed in each orbital is known as the

Pauli exclusion principle.

When filling degenerate orbitals, electrons fill them singly first, with parallel spins is known as

Hund's rule

An orbital that penetrates into the region occupied by core electrons is ______ shielded from nuclear charge than an orbital that does not penetrate and therefore has a _____ energy.

Less, Lower

The element that corresponds to the electron configuration 1s²2s²2p⁶3s²3p⁶4s¹3d⁵ is

chromium

Give the ground state electron configuration for Se.

[Ar]4s²3d¹⁰4p⁴

Give the ground state electron configuration for I.

[Kr]5s²4d¹⁰5p⁵

Give the ground state electron configuration for Sr.

[Kr]5s²

Give the complete electronic configuration for Mn.

1s²2s²2p⁶3s²3p⁶4s²3d⁵

Identify the element that has a ground state electronic configuration of [Kr]5s²4d⁵.

Tc

The Pauli Exclusion Principle states that

no two electrons in the same atom can have the same four quantum numbers.

What does an electron that penetrates another orbital mean

The electron has a higher probability of being found close to the nucleus

How many valence electrons do the alkaline earth metals possess?

2

How many valence electrons do the halogens possess?

7

Are the alkali metals reactive?

Yes, since they only are looking to lose 1 VE

Do metals tend to gain or lose electrons

Lose

What color is chlorine gas

greenish-yellow

Describe the reaction of the noble gases with metals.

Inert

Describe the reaction of the alkali metals with non-metals.

Vigorous

Halogens can react with each other to form

Covalent Bonds

Identify a characteristic of halogens.

powerful oxidizing agents - Halogens (Group 17: F, Cl, Br, I) have 7 valence electrons and need only 1 more electron to achieve a stable octet. Because they readily gain electrons, they cause other substances to lose electrons (be oxidized).

What direction does atomic radius increase

Down and to the Left

Are Cations smaller or larger than their neutral atom

Small

Predict the charge that an ion formed from sulfur would have.

2-

Predict the charge that an ion formed from sodium would have.

1+

A cation of +2 indicates that an element has

lost two electrons

Are cations or anions larger

Anions

How do you determine the order of ionic radii (size of ions)?

• Cations (+) are smaller than their neutral atoms

• Anions (−) are larger than their neutral atoms

• More positive charge → smaller ion

• More negative charge → larger ion

• More energy levels (down a group) → larger ion

The ________ is a change in energy associated with gaining an electron in the gaseous state for an atom or ion.

electron affinity

Does ionization energy involve gaining or losing an electron

Losing

Does electron affinity involve gaining or losing an electron

Gaining

What is first ionization energy?

Energy required to remove the first (outermost) electron from a neutral gas-phase atom.

X(g)→X+(g)+e−

Depends on shielding, nuclear charge, and atomic radius.

Why are later ionization energies much higher than the first?

Later ionization energies remove electrons from positively charged ions, where:

• fewer electrons = less shielding

• stronger attraction to nucleus

• may involve removing core electrons after valence electrons are gone

Result: ionization energy increases sharply after valence electrons are removed.

Diamagnetic

No unpaired electrons

Paramagnetic

Unpair electrons

How do you write ground-state electron configurations for transition metals

• Fill orbitals using Aufbau order:

  • 1s → 2s → 2p → 3s → 3p → 4s → 3d → 4p

• Write configuration normally, but remember:

  • 4s fills before 3d

  • 4s is removed before 3d when forming ions

• For transition metals (neutral atoms):

  • Keep 4s before 3d in writing

  • Example: Zn = [Ar] 4s² 3d¹⁰

• For cations:

  • Remove electrons from 4s first, then 3d

  • Example: Fe²⁺ = [Ar] 3d⁶ (4s removed first)

density formula

D=M/V

What is precise

• How close repeated measurements are to each other

• Think: “Are results consistent?”

What is accurate

• How close a measurement is to the true or accepted value

• Think: “Is it correct?”

If the water level is between 5 and 6 with 0 line between, how do write the fill level

5.0 to 6.0

What is an exact number

a value that is known with complete certainty and has no uncertainty or error.

Avogadro’s number is treated as exact in modern definitions (for practical calculations)

• 12 atoms

• 6 molecules

multiplication and division sig rule

least # of sig fig

addition and division sig fig rule

least decimal

multi step sig fig rules

• Final step decides rounding

• Never round early

M = mega exponent form

10^6

G = giga exponent form

10^9

k = kilo exponent form

10³

deca = da exponent form

10^1

deci = d exponent form

10^-1

centi = c exponent form

10^-2

milli = m exponent form

10^-3

micro = µ exponent form

10^-6

nano exponent form

10^-9

pico exponent form

10^-12

Are solids, liquids, or gases compressible

Gases

proton neutron and electron in increasing mass order

electron proton neutron

whats a molecule

2 or more chemicals joined together

which state of matter has no definite shape and a definite volume

liquid

The statement, "In a chemical reaction, matter is neither created nor destroyed" is called

the Law of Conservation of Mass.

The mass number is equal to

the sum of the number of protons and neutrons.

what is the relation of subatomic particles in a neutral atom

A neutral atom contains the same number of protons and electrons.

Who determined that the mass of an atom is concentrated in a very small space.

Rutherford's Gold Foil Experiment

When two elements form two different compounds, the masses of element B that combine with 1 g of element A can be expressed as a ratio of small whole numbers. Which law does this refer to?

Law of Multiple Proportions

Which subatomic particle increases the size

electron

how to handle naturally forming isotopes q’s

add up amounts x percentages

How do you convert between mass, moles, and atoms?

• moles ↔ particles (atoms/molecules):
  1 mol = 6.022 × 10²³ particles (Avogadro’s number)

• mass ↔ moles:

  moles=mass (g) / molar mass (g/mol)

Conversion pathway order

GMA or AMG

Which sample has the fewest atoms when all masses are equal (10.0 g each)?

Higher molar mass = fewer moles = fewer atoms

Just pick the element with the largest molar mass

The vertical height of a wave is called

amplitude

Which of the following visible colors of light has the highest frequency?

blue

When waves of equal amplitude from two sources are out of phase when they interact, it is

called

destructive interference.

When a wave encounters an obstacle or a slit that is comparable in size to its wavelength, it

bends around it. This characteristic is called

diffraction

what occurs as the energy of a photon increases

The wavelength gets shorter

How do you determine the possible sublevels (l values) for any principal energy level n?

For any principal energy level n, the allowed sublevels are:

l = 0 to (n−1)

what does n stand for

principle quantum number

• Energy level (shell)

• Values: 1, 2, 3, 4, ...

• Higher n = higher energy, farther from nucleus

what does l stand for

angular momentum

• Sublevel type

• Values: 0 to (n − 1)

• Means:

  • 0 = s

  • 1 = p

  • 2 = d

  • 3 = f

what does ml stand for

magnetic quantum number

• Orbital orientation

• Values: −l to +l

• Determines how many orbitals exist in a sublevel

what does ms stand for

spin

• Values:

  • +½ (spin up ↑)

  • −½ (spin down ↓)

• Each orbital holds max 2 electrons with opposite spins

How many orbitals are contained in the third principal level (n = 3) of a given atom?

• s sublevel → 1 orbital

• p sublevel → 3 orbitals

• d sublevel → 5 orbitals

---

🔑 Step 3: Total orbitals 1+3+5=9

How many sublevels are contained in the second shell (n = 2) of a given atom?

2

Which of the following quantum numbers describes the shape of an orbital?

angular momentum quantum number

Which of the following quantum numbers describes the size and energy of an orbital

principal quantum number

Which of the following quantum numbers describes the orientation of an orbital?

spin quantum number

How many orbitals are present when l=3

7

How many nodes are found in a 3s orbital?

2

true or false the alkali metals are fairly unreactive

false

true or false Core electrons effectively shield outer electrons from nuclear charge

true

What is the rule for increasing ionization energy (IE) in the periodic table?

Across a period (left → right):

IE increases

• Stronger nuclear charge

• Smaller atomic radius

• Electrons held more tightly

Down a group (top → bottom):

IE decreases

• More energy levels (shielding increases)

• Outer electrons farther from nucleus

• Easier to remove electrons

Electron Affinity (EA) in Chemistry

Electron affinity is usually written as an energy change for adding an electron to a neutral atom in the gas phase:

🔑 Reaction form: X(g)+e− → X−(g)+energy

What are the periodic trends for metallic character?

Across a period (left → right):

Metallic character decreases

• Atoms hold electrons more tightly

• More nonmetal-like

Down a group (top → bottom):

Metallic character increases

• More shielding

• Larger atoms

• Easier to lose electrons