Unit 1-4 Chem

Vocabulary-style flashcards covering key chemistry terms.

What is an element?

A substance that contains only one type of atom.

What is a molecule?

A group of two or more atoms bonded together; can be two or more atoms of the same element or of different elements.

What is a compound?

A substance formed when atoms of two or more elements are chemically bonded in a fixed ratio.

What is a mixture?

A combination of two or more substances not chemically bonded together with no fixed composition.

What is a proton?

Positively charged subatomic particle (P+), located in the nucleus.

What is a neutron?

Electrically neutral subatomic particle (N0) in the nucleus.

What is an electron?

Negatively charged subatomic particle (e−) outside the nucleus, arranged in energy levels.

What is the mass number.

Total number of protons and neutrons in the nucleus; usually larger than the atomic number.

What is the atomic number?

Number of protons in the nucleus; in a neutral atom, equal to the number of electrons.

What is an ion?

A charged particle formed when an atom loses or gains electrons.

What is a cation?

Positively charged ion formed when an atom loses electrons.

What is an anion?

Negatively charged ion formed when an atom gains electrons.

What is an isotope?

Atoms of the same element with different numbers of neutrons, same number of protons.

What is a group?

A vertical column; elements in a group have the same (or similar) valence electrons.

What is a period?

A horizontal row; indicates the number of electron shells in the atoms.

What are the characteristics of metals?

High melting points, high electrical conductivity, high density, malleable, and ductile.

What are the characteristics of non-metals?

Low melting/boiling points, poor conductors of heat and electricity, brittle.

What is the atomic radius?

Distance from the nucleus to the outermost valence electrons; a measure of atomic size.

What is the atomic radius trend across a period L→ R?

Generally decreases from left to right due to increasing nuclear attraction.

What is the atomic radius trend down a group T→B?

Generally increases down a group as new electron shells are added.

What is ionisation energy?

Energy required to remove one electron from an atom to form a cation.

What is the ionisation energy trend across a period L→R?

Generally increases from left to right as nuclear attraction increases.

What is the ionisation energy trend down a group T→B.

Generally decreases down a group due to increasing electron shielding.

What is electronegativity?

Tendency of an atom to attract electrons in a chemical bond.

What is the electronegativity trend across a period L→R.

Generally increases from left to right with increasing nuclear charge.

What is the electronegativity trend down a group T→B.

Generally decreases down a group due to electron shielding.

Where metals are located on the periodic table?

Left side of the periodic table.

Where non-metals are located on the periodic table?

Right side of the periodic table.

What are the diatomic molecules?

H, N, F, O, I, Cl, Br.

What is the octect rule, who is in it.

Atoms want 8 valency. C N O F + Halogens.

What are the characteristics of ionic bonds?

Do not conduct electricity as solids; conduct electricity when molten or dissolved. High MP due to lattice, soluble in water.

What is the synthesis reaction?

A reaction where two or more substances combine to form a single product (A + B → AB).

What is the decomposition reaction?

A reaction where a compound breaks down into simpler substances (AB → A + B).

What is the combustion reaction?

A substance (usually hydrocarbon) reacts with oxygen to form CO2 and H2O.

What is the single displacement reaction?

A more reactive element replaces another element in a compound (A + BC → B + AC).

What is the double displacement reaxtion?

Ions in two ionic compounds exchange partners to form two new compounds (AB + CD → AD + CB).

How many electrons do halogens like to gain?

Halogens need 1 more electron to complete their octet.

Why is Be > B in ionisation energy?

Be 2s² is full and stable; B 2p¹ is higher energy and easier to remove.

What is the trend of metallic character across a period?

Decreases → less willing to lose electrons.

What is the trend of metallic character down a group?

Increases → electrons easier to lose.

What is the reactivity trend of metals down a group?

Increases → electrons easier to lose.

What is the reactivity trend of non-metals down a group?

Decreases → electrons harder to gain.

What is the melting/boiling point trend in ionic solids?

Increases with ion charge and smaller ions → stronger lattice.

What is the melting point trend in covalent molecular solids?

Low → weak intermolecular forces.

What is the conductivity of ionic solids?

Solid: no; molten/aqueous: yes → ions free to move.

What is the conductivity of metals?

Yes → delocalized electrons free to move.

What is the solubility of covalent network solids?

Usually insoluble → strong covalent lattice.

What affects the melting point in metallic solids?

Number of delocalized electrons, strength of metal–metal bonds.

What is the difference between covalent molecular vs covalent network?

Molecular: weak intermolecular forces, low MP/BP; Network: strong covalent bonds, very high MP/BP.

Why does oxygen have lower ionisation energy than nitrogen?

N 2p³ is half-filled (stable); O 2p⁴ has paired electron → repulsion, easier to remove.

What is Pauli's Exclusion Principle?

In an atomic orbital, can contain at most 2e- at any time. Opposite spins.

What is Hund's Rule?

When filling orbitals of the same energy, electrons spread out and occupy empty orbitals before pairing up.

What is the Aufbau Principle?

Electrons fill the lowest energy levels first before moving to higher ones.