chem

CHEMISTRY

ATOMS:

Element: is a pure substance that cannot be broken down.

Compound: made by chemically combining two or more different atoms.

Mixture: made by physically mixing two or more substances and can be separated.

Proton: positive charge, mass is 1, position is located in the nucleus.

Neutron: neutral charge, mass is 1, position is located in the nucleus.

Electron: negative charge, smallest mass, position is located in the electron shells.

Isotopes: are atoms of the same element that have the same number of protons but a different number of neutrons.

Mass number = neutrons + protons

Protons = atomic number

Electrons = protons (except for ions)

Neutrons = mass number - protons

Isotopic symbols: on top is the mass number and the bottom is the protons/atomic number.

Electrons are arranged in electron shells around the nucleus, based on energy levels. The first shell must have a maximum of 2 electrons then the rest have a maximum number of 8 electrons.

The number of valence electrons in an element connects to the group of the periodic table because as you move across the group, the number of valence electrons increases.

Ion: is an atom with an uneven number of protons and electrons, and to achieve stability, the atom will either gain or lose electrons to fill or empty its valence shell. 

Metals form cations and lose electrons

Non-metals form anions and gain electrons.

Ionic compound: is when an anion and a cation are attracted to each other due to an electrostatic force, they will undergo chemical bonding and form an ionic compound. 

Combustion and Corrosion Reactions:

Physical Change: A change in the state or appearance of a substance, but no new substance is formed. The composition remains the same (e.g., melting ice, dissolving salt in water).

Chemical Change: A change where a new substance is formed. This involves the breaking and forming of chemical bonds (e.g., burning wood, rusting iron).

Reactants are the starting substances in a chemical reaction. They are on the left side of the equation.

Products are the new substances formed in the reaction. They are on the right side of the equation

(s) = solid

(l) = liquid

(g) = gas

(aq) = aqueous (dissolved in water)

In balancing a chemical equation, you make sure the number of atoms for each element is the same on both sides of the equation.

According to the law of conservation of mass, mass cannot be created or destroyed in a chemical reaction. The total mass of the reactants must equal the total mass of the products.