Definitions For Topic 1 Key Concepts In Chemistry⬆️ Flashcards
What is an anion?
A negatively charged ion formed when an atom gains at least one electron.
Anions are often involved in ionic compounds and play a key role in chemical reactions.
Define an atom.
The smallest part of an element that can exist, and all substances are made up of atoms.
Atoms consist of a nucleus surrounded by electrons.
What is the atomic nucleus?
A positively charged object composed of protons and neutrons at the center of every atom with electrons orbiting it.
The atomic nucleus contains most of the atom’s mass.
What does atomic number indicate?
The number of protons in the nucleus.
The atomic number uniquely identifies an element.
What is Avogadro’s constant?
The number of atoms, molecules, or ions in a mole of a given substance.
Avogadro’s constant is approximately 6.022 x 10^23.
Define a cation.
A positively charged ion formed when an atom loses at least one electron.
Cations are typically formed from metals in chemical reactions.
What is a compound?
A substance made up of two or more types of atoms chemically combined together.
Compounds can be ionic or covalent in nature.
What does concentration refer to?
The amount of substance (e.g. the mass) in a certain volume of a solution.
Concentration is often expressed in molarity (moles per liter).
Define a conductor.
A material that contains charged particles which are free to move to carry electrical or thermal energy.
Metals are common examples of good conductors.
What is the conservation of mass?
A law which states that no atoms are lost or made during a chemical reaction so the mass of the products equals the mass of the reactants.
This principle is fundamental in chemical equations.
What is a covalent bond?
A shared pair of electrons between two non-metals.
Covalent bonds result in the formation of molecules.
Describe the Dalton model.
Dalton described atoms as solid spheres, stating that different spheres made up the different elements.
This model was one of the first to propose a theory of atomic structure.
What is diamond?
A giant covalent structure made up of carbon atoms, each forming four covalent bonds with four other carbon atoms.
Diamond is known for its hardness and is used in cutting tools.
What is an electron?
Negatively charged subatomic particle which orbit the nucleus at various energy levels
Very small relative mass (negligible)
What is an electron shell?
Different energy levels in atoms occupied by electrons
What are electrostatic forces?
The strong forces of attraction between oppositely charged ions
Define an element.
A substance made up of only one type of atom
What is an empirical formula?
The simplest whole number ratio of atoms of each element in a compound
What are fullerenes?
Molecules of carbon atoms with hollow shapes, based on hexagonal rings
Examples include graphene and C60
What is a giant covalent molecule?
Molecules containing many atoms covalently bonded together
What is graphene?
A single layer of graphite with properties that make it useful in electronics and composites
Describe graphite.
A giant covalent structure made up of carbon atoms forming layers of hexagonal rings
What is a group in the periodic table?
A column of the periodic table where elements have similar chemical properties
What are intermolecular forces?
The forces which exist between molecules that impact physical properties like boiling/melting point
What is an ion?
An atom or molecule with an electric charge due to the loss or gain of electrons
What is an ionic bond?
The bond formed between oppositely charged ions when a metal atom loses electrons and a non-metal gains them
Define an ionic compound.
Chemical compound formed of oppositely charged ions, held together by strong electrostatic forces
What is an isotope?
Atoms of the same element with the same number of protons but a different number of neutrons
What is a lattice?
A repeating regular arrangement of atoms/ions/molecules occurring in crystal structures
What is a limiting reactant?
The reactant that is completely used up since it limits the amount of products formed.
Define mass number.
The total number of protons and neutrons in the nucleus.
What is a metallic bond?
The bonds present in metals between the positive metal ions and negatively charged electrons.
What are metals?
Elements that react to form positive ions. Found to the left and towards the bottom of the periodic table.
What is the unit for amount of substance?
Mole. The symbol for the unit mole is mol.
What is a molecular formula?
The actual ratio of atoms of each element present in a compound.
Define a molecule.
A group of at least two atoms held together by covalent bonds.
What is a neutron?
Neutral subatomic particle present in the nucleus of the atom. Relative mass of 1.
What are non-metals?
Elements that react to form negative ions. Found towards the right and top of the periodic table.
What is a period in the periodic table?
A row of the periodic table. Elements in the same period have the same number of electron shells.
What is the periodic table?
Table of elements arranged in order of increasing atomic number and such that elements with similar properties are in the same column (group).
Define polymers.
Large long-chain molecules made up of lots of small monomers joined together by covalent bonds.
What is a proton?
Positively charged subatomic particle present in the nucleus of the atom. Relative mass of 1.
What is relative atomic mass?
An average value that takes into account the abundances of the isotopes of the element.
Define relative formula mass.
The sum of the relative atomic masses of the atoms in the numbers shown in the formula.
What are simple molecules?
Molecules containing a fixed number of atoms covalently bonded together.
What are subatomic particles?
Particles smaller than an atom. Protons, neutrons and electrons are the three most common subatomic particles.
