Honors Atoms and Elements

atom

The smallest unit of matter that retains the properties of an element, consisting of a nucleus surrounded by electrons.

proton

A positively charged subatomic particle found in the nucleus of an atom, contributing to the atomic mass and identity of an element.

neutron

A subatomic particle that has no charge and is found in the nucleus of an atom. Neutrons play a crucial role in stabilizing the nucleus.

electron

A negatively charged subatomic particle that orbits the nucleus of an atom, playing a crucial role in chemical bonding and reactions.

nucleus

The central region of an atom, composed of protons and neutrons, which contains most of the atom's mass and positively charged particles.

atomic mass

The weighted average mass of an atom's isotopes, measured in atomic mass units (amu), reflecting both the number of protons and neutrons.

atomic number

The number of protons in the nucleus of an atom, which determines the element's identity and its position on the periodic table.

element/chemical symbol

a one or two letter abbreviation that represents the chemical element. The first letter is always capitalized, if there is a second letter it is lowercase (Na, Cl, Mg)

Periodic Table

A table arrangement of chemical elements organized by increasing atomic number, with rows called periods and columns called groups.

groups

Vertical columns in the Periodic Table that categorize elements with similar properties and similar valence electron configurations.

periods

horizontal rows in the Periodic Table that categorize elements according to their atomic number and properties.

coefficient

A numerical value placed in front of a chemical formula to indicate the number of molecules or moles of that substance in a reaction.

subscript

A number written below and to the right of a chemical symbol in a formula, indicating the number of atoms of that element in a molecule.

ion

An atom or molecule that has gained or lost one or more electrons, resulting in a net electrical charge.

element

A pure substance that cannot be broken down into simpler substances and consists of only one type of atom.

chemical formula

A symbolic representation of a substance that indicates the elements present and the ratio of atoms in the compound. (CO2)

molecule

A group of two or more atoms bonded together, representing the smallest fundamental unit of a chemical compound.

compound

A substance formed when two or more elements chemically bond together in fixed proportions.

ball and stick model

A three-dimensional representation of molecules that shows the bonds between atoms as sticks and the atoms as spheres.

alkali metals

Elements in Group 1 of the periodic table, highly reactive with water and oxygen.

alkaline Earth metals

Elements in Group 2 of the periodic table, they are reactive but less so than alkali metals and are known for forming basic oxides and hydroxides.

post-transition metals

Elements in groups 13 to 16 of the periodic table, typically characterized by being softer and having lower melting points than transition metals.

transition metals

Elements found in the d-block of the periodic table, characterized by their ability to form variable oxidation states and colored compounds.

metalloids

Elements with properties intermediate between metals and nonmetals, often displaying mixed characteristics such as conductivity and brittleness.

non-metals

Elements that lack metallic properties, typically poor conductors of heat and electricity, and often found in gaseous or solid forms at room temperature.

Halogens

Elements in Group 17 of the periodic table, known for being highly reactive and forming salts with metals. They exist in all three states of matter and include fluorine, chlorine, bromine, iodine, and astatine.

lanthanides

A series of 15 metals from cerium to lutetium, found in the f-block of the periodic table, known for their similar properties and high reactivity.

lewis structure

A diagram that represents the bonding between atoms in a molecule and the lone pairs of electrons that may exist. It uses dots to represent electrons and lines to indicate bonds.

chemical equation

A mathematical statement that represents a chemical reaction, showing the reactants and products along with their relative amounts. It illustrates the conservation of mass by balancing the number of atoms on both sides.