Term 1 Chemistry Flashcards
define aqueous solution
A mixture in which a substance is dissolved in water
If a substance is in an aqueous solution, it is represented using the symbol (aq).
define atom
The smallest particle of an element
An atom is made up of even smaller subatomic particles – protons, neutrons and electrons.
define balanced
An equation with equal numbers of atoms of each element on either side
A balanced chemical equation follows the law of conservation of matter.
define chemical bond
An attractive force that holds atoms together
A chemical bond can hold atoms together in a molecule or lattice.
define chemical equation
A representation of how a chemical reaction rearranges atoms
A chemical equation can be represented in words, symbols, or diagrams.
define chemical formula
A symbol that shows the chemical composition of a molecule or lattice
The chemical formula for water is H2O as each molecule has two hydrogen atoms and one oxygen atom.
define chemical reaction
The re-arrangement of atoms to form one or more new substances
In a chemical reaction the number of each type of atom remains the same.
define chemical symbol
One or two letters used to represent an element
The first letter of a chemical symbol is uppercase and the second letter is lowercase.
define coefficient
A number placed before a formula in a chemical equation
A coefficient is placed before a formula, whereas a subscript is used within it.
define compound
Two or more elements joined together by chemical bonds
e.g. The compound sodium chloride consists of sodium and chloride atoms chemically bonded together.
define element
A substance made up of only one type of atom
e.g. Gold is an element in which every atom has 79 protons.
Law of Conservation of Matter
The rule that the number of atoms in a chemical reaction remains the same
During all chemical reactions, the total number of atoms of each element doesn’t change.
define molecule
A group of atoms bonded together
e.g. An oxygen gas molecule is made up of two oxygen atoms bonded together.
define physical change
A change in matter that does not form new substances
Physical changes include breaking, mixing and changing the state of a substance.
define product
A substance formed by a chemical reaction
In a chemical equation, the products are located to the right of the arrow.
define reactant
A substance that reacts to form one or more new substances
In a chemical equation, the reactants are located to the left of the arrow.
define reactive
Tending to take part in chemical reactions
Sodium is one of the most reactive elements in the periodic table.
define state symbol
A symbol used to indicate the state of matter of a substance
e.g. The state symbol (s) is used for solids, (l) for liquids, (g) for gases, or (aq) for aqueous solutions.
define subscript
A number used to show how many atoms of an element are present
e.g. The subscript 2 in H2O shows there are 2 hydrogen atoms present in water.
define symbol equation
A chemical equation that uses chemical formulas to represent substances
e.g. A symbol equation would represent ammonium as the chemical formula NH₃.
define unbalanced
An equation with an unequal number of atoms on either side
Unbalanced equations must be balanced so that they follow the law of conservation of matter.
define word equation
A chemical equation that uses names to represent substances
A word equation would represent ammonium in an equation as the word ammonium.
define atomic number
The number of protons in an atom
Each element has a unique atomic number. A hydrogen atom has 1 proton so its atomic number is 1.
define charge
An electrical property of matter
A particle can have a positive charge, a negative charge or no charge (neutral).
define electron
A very small subatomic particle with negative charge
Electrons are located outside the nucleus of an atom.
define electron cloud model
A model of the atom in which electrons move freely
In the electron cloud model, electrons may be anywhere in the electron cloud at any time.
define ion
An atom or molecule with a net charge
A neutral atom that gains an electron becomes a negative ion with a charge of –1.
define isotope
A variation of an element with a certain number of neutrons in each atom
e.g. Carbon-14 is an isotope of carbon that has two more neutrons than the carbon-12 isotope.
define mass number
The number of protons and neutrons in an atom
Atoms of an element can have more or less neutrons, changing their mass numbers.
define net charge
The overall electrical charge of a particle
The net charge of an atom is the number of protons minus the number of electrons.
define neutral particle
A particle with zero net charge
Neutrons are neutral. An atom is neutral when it has an equal number of protons and electrons.
define neutron
A large subatomic particle with no charge
Neutrons are located in the nucleus of an atom.
nucleus
The central part of an atom, with an overall positive charge
Nuclei are made up of positively charged protons and uncharged neutrons.
define planetary model
A model of the atom in which electrons move in defined orbits
In the planetary model, electrons circle the nucleus like planets orbiting the Sun.
define positive ion
An atom or molecule with a net positive charge
With more protons than electrons, these ions have an overall positive charge.
define negative ion
An atom or molecule with a net negative charge
With more electrons than protons, these ions have an overall negative charge.
define proton
A large subatomic particle with positive charge
Protons are located in the nucleus of an atom.
define radiation
The energy or particles released during radioactive decay
The three main types of radiation are alpha particles, beta particles and gamma waves.
define radioactive decay
The process of unstable atoms releasing radiation
Releasing radiation makes the atom’s nucleus more stable.
define stable isotope
An isotope in which the nucleus is not likely to break apart
e.g. Carbon-12 is a stable isotope of carbon that has equal numbers of protons and neutrons.
define subatomic particle
A particle of matter that is smaller than an atom
Protons, neutrons and electrons are types of subatomic particles.
define unstable isotope
An isotope in which the nucleus is likely to break apart
Carbon-14 is an unstable isotope of carbon because it has too many neutrons in the nucleus.
Describe the location of subatomic particles in an atom
Protons and neutrons are located in the densely packed nucleus at the centre of the atom. The nucleus is tiny compared to the size of the whole atom, which is mostly empty space.
Electrons are located in the empty space around the nucleus, randomly whizzing around.
Compare the subatomic particles by their mass and electrical charge
Protons
- Mass = 1
- Charge = positive
Neutrons
- Mass = 1
- Charge = neutral
Electrons
- Mass = 1/1840
- Charge = negative
Describe how the number of protons determines an element’s atomic number
The number of protons is the same as the atomic number of the element. So as the number of protons increases by 1, so does the atomic number.
Explain the relationship between protons and electrons in neutral atoms
In a neutral atom, the charges of protons and electrons are equal in size but opposite (positive or negative), they balance each other out. This means that the atom as a whole has an overall charge of zero.
Describe the repulsion and attraction of charged particles
Opposite charges attract
Like charges repel
Explain how the number of neutrons affects the mass number of an atom
Each time a neutron is added, the mass number increases by 1.
This is because the mass number is the total number of protons and neutrons in the nucleus.
Describe how mass number relates to isotopes
Atoms of the same element with different mass numbers are known as isotopes. Different isotopes of an element are identified by their mass numbers – for example, as carbon-12 or carbon-14. Each isotope may be stable or unstable
Compare types of radiation
Explain how radioactive decay results in stable atoms
Unstable atoms release radiation in a process called radioactive decay. Releasing radiation makes the atom’s nucleus more stable.
Describe what is a chemical reaction
A chemical reaction is the transformation of one or more substances into new substances.
