(Shrinked) Chapter 3 Test Chem

Law of conservation of mass

the law that states that mass cannot be created or destroyed in ordinary chemical and physical changes

Law of multiple proportions

the law that states that when two elements combine to form two or more compounds, the mass of one element that combines with a given mass of the other is in the ratio of small whole numbers

Electron

a subatomic particle that has a negative electric charge

Nucleus

an atom's central region, which is made up of protons and neutrons

Proton

a subatomic particle found in the nucleus of an atom, which has a positive charge

Neutron

a subatomic particle found in the nucleus of an atom, which has no electric charge

Atomic number

the number of protons in the nucleus of an atom; the atomic number is the same for all atoms of an element

Isotope

variants of a chemical element that have the same number of protons but different numbers of neutrons

Dalton's atomic theory

a theory that states all matter is composed of extremely small particles called atoms, which cannot be subdivided, created, or destroyed

Dalton's first principle

Atoms of a given element are identical in their physical and chemical properties

Dalton's second principle

Atoms of different elements differ in their physical and chemical properties

Dalton's third principle

Atoms of different elements combine in simple, whole-number ratios to form compounds

Dalton's fourth principle

In chemical reactions, atoms are combined, separated, or rearranged but never created, destroyed, or changed

Cathode ray Tube (CRT)

a device used by J.J. Thomson to discover electrons by pumping air out of a glass tube and applying voltage to two metal plates called electrodes

Anode

the electrode attached to the positive terminal of voltage in a cathode ray tube, which has a positive charge

Cathode

The other electrode which had a negative charge because it was attached to a negative terminal.

Plum Pudding Model

Rutherford's design of an atom.

Gold Foil Experiment

An experiment that led to the discovery of the nucleus.

Alpha Particles

A beam of small, positively charged particles aimed at a thin gold foil.

Radius of an Atom

1/10000 of the radius of the atom.

Coulomb's Law

States that the closer two charges are, the greater the force between them.

Orbital

A region in an atom where there is a high probability of finding electrons.

Electromagnetic Spectrum

All of the frequencies or wavelengths of electromagnetic radiation.

Ground State

The lowest energy state of a quantized system.

Excited State

A state in which an atom has more energy than it does at its ground state.

Quantum Number

A number that specifies the properties of electrons.

Pauli Exclusion Principle

States that two particles of a certain class cannot be in the exact same energy state.

Electron Configuration

The arrangement of electrons in an atom.

Aufbau Principle

States that the structure of each successive element is obtained by adding one proton to the nucleus and one electron to the lowest-energy orbital available.

Hund's Rule

States that for an atom in the ground state, the number of unpaired electrons is the maximum possible and these unpaired electrons have the same spin.

Bohr's Model

Confines electrons to energy levels.

Quantum of Energy

The difference in energy between two energy levels.

Light

Acts as both a wave and a particle.

atomic mass

the mass of an atom expressed in atomic mass units

molar mass

the mass in grams of 1 mol of a substance

Avogadro's number

6.022 × 10^23, the number of atoms or molecules in 1 mol

Atomic Number (Z)

Number of protons in the nucleus. Defines the element.

Mass Number (A)

Total number of protons + neutrons.

Quantum Model

Electrons are not fixed in paths like planets; instead, they exist in regions of probability called orbitals.

Atomic Mass Unit (amu)

A relative unit based on carbon-12.

The Mole (mol)

SI unit for amount of substance.

Negatively charged subatomic particle

Electron (carries a negative charge, mass ≈ 1/2000 of a hydrogen atom)

Positively charged subatomic particle

Proton (carries a positive charge, defines atomic number)

Gold foil experiment result

Most particles passed through the foil (atoms are mostly empty space)

Dalton's atomic theory statement

Atoms of the same element are identical in size, mass, and properties

Isotopes definition

Atoms of the same element with different numbers of neutrons (different masses)

Conservation of mass model

Matter is conserved in chemical changes (mass is neither created nor destroyed)

Cathode tube current flow

From cathode to anode (basis of electron discovery)

Law of definite proportions

Part of Dalton's atomic theory (compounds contain elements in fixed ratios)

Rutherford's conclusion

Atom contains a dense, positively charged nucleus (explains scattering in gold foil experiment)

Mass number example

13 protons + 14 neutrons = 27 (neutral isotope with 13 electrons)

Dalton's atom model

Atoms are indivisible and indestructible (later revised with subatomic particles)

Neutron mass

About equal to the mass of a proton (≈ 1 amu)

Electron mass

≈ 1/2000 of a hydrogen atom (tiny compared to proton/neutron)

Isotopes (different atomic masses)

Same element, different mass numbers due to varying neutrons