atomic theory flashcards

What is matter?

anything that has mass and takes up space

Pure substance made of only one type of atom

element

Pure substance made of 2+ elements chemically bonded

compound

Physical combination of substances, not chemically bonded

Mixture

Smallest unit of an element that retains its properties

Atom

This particle has a positive charge and mass of ~1 amu

Proton

This particle has no charge and mass of ~1 amu

Neutron

This particle is negatively charged and found outside the nucleus

Electron

Where are protons and neutrons located?

in the nucleus of the atom

Where are electrons located?

In the electron cloud

Atomic number equals…

The number of protons

Mass number equals…

Protons + neutrons

Atoms of the same element with different numbers of neutrons

Isotopes

Atoms with a charge

Ions

Ion with a positive charge

Cation

Ion with a negative charge

Anion

Greek philosopher who first proposed atoms (400 BCE)

Democritus

Philosopher who believed matter was continuous, not atomic (Fire, Water, Earth, Air)

Aristotle

Scientist who proposed the first modern atomic theory (1803)

John Dalton

Who discovered the electron?

J.J. Thomson

What experiment led Thomson to discover electrons?

Cathode ray tube

Thomson's atomic model

Plum pudding model

Who discovered the nucleus?

Ernest Rutherford

Experiment that discovered the nucleus

Gold foil experiment

What did Rutherford's experiment show?

Atom is mostly empty space, small dense positive nucleus

Who proposed electrons move in fixed orbits (1913)?

Niels Bohr

Bohr's model compared electrons to…

Planets orbiting the sun

Modern atomic model

Quantum Mechanical Model

Who developed the electron cloud model?

Schrödinger.

What does Heisenberg's uncertainty principle state?

Cannot know both position and velocity of an electron.

Wave-particle duality was proposed by…

de Broglie

The dense, positively charged center of the atom

Nucleus

Most of the atom's volume is…

Empty space

Periodic Law

Properties of elements repeat in a pattern

Columns on the periodic table are called…

Groups (or families)

Rows on the periodic table are called…

Periods.

Elements in the same group have the same number of…

Valence electrons.

Valence electrons determine…

Reactivity of an element

Elements on the left side of the periodic table

Metals

Elements on the right side of the periodic table

Nonmetals

Elements with properties of both metals and nonmetals

Metalloids

Group 1 elements are called…

Alkali metals

Group 2 elements are called…

Alkaline earth metals

Group 17 elements are called…

Halogens

Group 18 elements are called…

Noble gases

Metals tend to form…

Cations (lose electrons)

Nonmetals tend to form…

Anions (gain electrons)

The average mass of all isotopes of an element

Atomic mass

Formula for atomic mass

Σ (isotope mass × % abundance)

Type of bond formed when electrons are transferred

Ionic bond

Type of bond formed when electrons are shared

Covalent bond

Type of bond with a "sea of electrons"

Metallic bond

The first energy level can hold how many electrons?

2

The second energy level can hold how many electrons?

8

s-orbital can hold…

2 electrons

p-orbital can hold…

6 electrons

d-orbital can hold…

10 electrons

f-orbital can hold…

14 electrons

Aufbau principle

Fill lowest energy orbitals first.

Hund's rule

Electrons fill orbitals singly before pairing.

Pauli exclusion principle

Max 2 electrons per orbital, opposite spins

Electron configuration of oxygen (8e⁻)

1s² 2s² 2p⁴

Lowest energy state of an atom

Ground state

When electrons absorb energy and move to higher levels

Excited state

Light particle (energy packet)

Photon

Study of light absorbed/emitted by atoms

Spectroscopy

Each element's unique light fingerprint

Emission spectrum

Unstable nuclei releasing particles/energy

Radioactivity

Alpha particle contains…

2 protons + 2 neutrons

Which radiation has the lowest penetration?

Alpha

Which radiation is an emitted electron?

Beta

Which radiation has the highest penetration?

Gamma

Time for half of a radioactive sample to decay

Half-life

Equation for light energy

E = hν

Equation relating wavelength and frequency

c = λν

Electronegativity

Atom's pull on shared electrons

Ionization energy

Energy required to remove an electron

Trend: Atomic radius across a period

Decreases

Trend: Atomic radius down a group

Increases

Trend: Ionization energy across a period

Increases

Trend: Ionization energy down a group

Decreases

Trend: Electronegativity across a period

Increases

Trend: Electronegativity down a group

Decreases

What does Dalton's theory say about atoms of the same element?

They are identical

What part of Dalton's theory is incorrect today?

Atoms are indivisible and identical

Who showed that atoms have smaller particles?

Thomson (electrons)

Who proved the existence of a nucleus?

Rutherford

Who explained atomic spectra with energy levels?

Bohr

Which model is most accurate today?

Quantum Mechanical Model

What is the charge of the nucleus?

Positive

What does the periodic table tell us about each element?

Symbol, atomic number, atomic mass.

The electron cloud is based on…

Probability of finding electrons

Which principle explains why electrons don't all cram into 1 orbital?

Pauli exclusion principle

The modern view of the atom combines which two ideas?

Wave-particle duality & probability (quantum mechanics).

What part of the atom determines chemical reactivity?

Valence electrons

Electrons in the outermost shell are called…

Valence electrons

Electrons not in the outermost shell are called…

Core electrons

The region where electrons are most likely to be found

Electron cloud

The probability-based region describing electron location

Orbital

Another name for the electron cloud model

Quantum mechanical model