Chemical Reactions and Changes

A type of chemical bond where atoms share electrons to achieve a stable electron configuration. The number of shared electrons determines the type of bond: single bond (2 electrons), double bond (4 electrons), or triple bond (6 electrons).

A chemical reaction where heat energy is released into the surroundings. These reactions often feel hot to the touch.

A chemical reaction that absorbs heat energy from the surroundings. These reactions often feel cold to the touch.

The substance that gets dissolved in a solvent to form a solution. It is usually present in a smaller amount compared to the solvent.

The liquid that dissolves a solute to form a solution. It is usually present in a larger amount compared to the solute.

A solution that cannot hold any more solute at a given temperature. Adding further solute will result in it not dissolving.

A chemical change that results in the formation of a new solid substance. It is typically observed as a cloudy or opaque appearance in a clear liquid.

A chemical change that results in the production of bubbles of gas in a liquid. It is often accompanied by fizzing or bubbling.

A chemical formula shows the elements present in a substance and their ratio. For example, CO₂ represents carbon dioxide, indicating one carbon atom and two oxygen atoms.

Prefixes like 'di-' or 'tri-' in chemical formulas tell us how many atoms of a specific element are present. For example, in carbon dioxide (CO₂), 'di-' indicates two oxygen atoms.

Valency represents the number of chemical bonds an atom can form. It's equal to the number of unpaired electrons in its outermost shell. For example, Group 1 elements have a valency of 1.

Transition metals don't have fixed group numbers, so their valency varies. It's indicated in Roman numerals. For example, in iron(III) chloride, the III signifies a valency of 3.

Group ions are groups of atoms that act as a single unit in a chemical formula. They have their own valency, which is shown in the data book. For example, nitrate (NO₃) has a valency of 1.

The swap and drop method uses valency to determine the chemical formula of a compound. The valency numbers are swapped and become the subscripts of the elements in the formula. For example, sodium (Na) with valency 1 and chlorine (Cl) with valency 1 form NaCl.

Noble gases, in Group 0 (or 8), are very unreactive non-metals that exist as gases at room temperature. They have a full outer shell of electrons, making them stable.

Elements exist in different states at room temperature. Some are gases (hydrogen, helium, oxygen, etc.), some are liquids (mercury, bromine), and most are solids.

Indicates the physical state of a substance in a chemical reaction. (s) represents solid, (l) represents liquid, (g) represents gas, and (aq) represents aqueous (dissolved in water).

A chemical equation is balanced when the number of atoms of each element on the reactants' side equals the number of atoms of that element on the products' side.

A type of chemical bond where two atoms share electrons to achieve a stable outer electron shell.

A type of chemical bond formed by the transfer of electrons between a metal and a non-metal, resulting in the formation of ions.

The arrangement of electrons in an atom's outer shell, which determines its chemical properties. Atoms strive to achieve a full outer shell for stability.

A strong attraction between atoms due to the sharing of electrons. Single, double, and triple bonds exist depending on the number of shared electrons.

A type of covalent bond where two pairs of electrons are shared between two atoms.

A type of covalent bond where three pairs of electrons are shared between two atoms.

The speed at which a chemical reaction occurs.

A substance that speeds up a chemical reaction without being used up itself.

The number of protons in an atom's nucleus.

The total number of protons and neutrons in an atom's nucleus.

Atoms of the same element that have the same number of protons but a different number of neutrons.

The average atomic mass of all naturally occurring isotopes of an element, taking into account their relative abundances.

An atom with a positive or negative charge due to a gain or loss of electrons.

A way to represent the distribution of electrons in an atom's shells, starting from the nucleus.

A simplified diagram that shows only the outermost shell of electrons in an atom.

A chart that organizes all the known elements according to their atomic number and chemical properties.

Elements in a compound are chemically combined, meaning they are joined together in a fixed ratio.

Metals are shiny, malleable (can be hammered into shapes), good conductors of heat and electricity. Non-metals lack these properties.

Elements in Group 1 of the periodic table are very reactive metals. They react vigorously with water to produce hydrogen gas and a metal hydroxide.

Transition metals exhibit the typical properties of metals, like being shiny, malleable, and good conductors of heat and electricity. They are generally less reactive than alkali metals.

Group 7 elements are reactive non-metals. They exist as diatomic molecules, meaning they exist in pairs.

A chemical formula shows us which elements are present in a substance and their ratio. For example, Carbon dioxide is CO2, indicating one carbon atom and two oxygen atoms.