Chemistry Vocabulary

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Atom = The smallest unit of matter; The basic unit of a chemical element. For example, Water (H2O) is made up of three atoms.



Colloid = Milk, Jell-O, glue and fog are colloids. The particles in a colloid are larger than ones found in solutions but smaller than ones found in suspensions. A Colloid is a homogeneous solution with intermediate particle size between a solution and a suspension. The colloid looks homogeneous to the naked eye. Colloids frequently appear "murky" or "opaque". The particles are large enough to scatter light. Fog is a colloid and you have experience with the way fog interacts with the light from car headlights. Colloids generally do not separate on standing. They are not separated by filtration. Many familiar substances, including butter, milk, cream, aerosols (fog, smog, and smoke), asphalt, inks, paints, glues, and sea foam are colloids.   

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Compound = a chemical substance that is formed from two or more elements, that bond in a fixed ratio. For example, water (H2O) is a compound that is composed of two hydrogen atoms for every oxygen atom. NH3, HCl, H2O2, SiO2, CH4, C2H2, and C2H4, are compounds. In contrast, O2 is not a compound because it is only made of one element. A compound is a pure substance.

Covalent Bonding is where 2 or more atoms bond by sharing their outer electrons. Generally, covalent bonds are made between nonmetal atoms. The result of this bond is a molecule. Covalent means, "sharing outer electrons". The nucleus of an atom is never changed or altered after bonding. Covalent bonding allows atoms to complete their outer shells.

Oxygen gas = O2

1 element, 2 atoms

Water = H2O

2 elements, 3atoms

Rubbing Alcohol = CH3 CH2 CH2 OH

3 elements, 12 atoms



Water Molecule

Alcohol Molecule

Electrons are stable subatomic particles that have a negative charge. They can be found in the shells of atoms outside the nucleus. A pair of electrons form a covalent bond between atoms.

An element is composed of one kind of atom. An element is a pure substance. An element cannot be broken down by physical or chemical means. 90 elements occur naturally on Earth. The other 19 or so are made in the lab. This means that in the universe, there are only 90 different types of atoms that make everything. C, H, O, N and P are the primary elements that make up living organisms.

Heterogeneous Mixture – is made up of visibly different substances or phases. Sand is a heterogeneous mixture. Heterogeneous mixtures are not uniform. There are pockets of one substance surrounded by pockets of different substances. A mixture of soil in water to make "mud" is heterogeneous. Likewise, a mixture of oil and water in salad dressing is heterogeneous. Beach sand is heterogeneous since you can see different colored particles.

Homogeneous Mixture – appears uniform and consistent throughout. Solutions and colloids are homogeneous mixtures. A lemonade drink is a homogeneous mixture, known as a solution. So is air. Both brass and glass are homogeneous mixtures/solutions.

Ion: a charged particle formed when an atom (or molecule) gains or loses one or more electrons.

Ionic Bonding: is a type of bonding in which ions are held together by the strong attraction of their opposite charges. The nucleus of an atom is never changed or altered after bonding.

Isotope: An isotope is an atom that has a different number of neutrons in its nucleus. Thus, an isotope has a different mass when compared to other atoms of the same element.

The octet rule states that after bonding... 

1) 8 electrons surround all atoms in columns 4-7. (After bonding)

2) Hydrogen's outer ring is completed with 2 electrons. (After bonding)

3) All atoms have a complete outer ring. All electrons are paired up. (After bonding)

4) All atoms have a complete outer ring like noble gasses. (After bonding)

In summary: Atoms share or transfer their electrons with other atoms to complete their outer ring and be like the noble gasses.

Mixture = a physical combination of 2 or more substances. Each substance maintains its own properties. The substances can be physically separated.

A molecule consists of two or more atoms that bond by sharing their outer electrons.

Hydrogen gas (H2) and water (H20) are examples of molecules.

A Precipitate is solid that comes out from a solution during a chemical reaction.

Precipitation is the separation of a solid from a solution during a chemical reaction.

Protons are stable subatomic particles that are found in the nucleus of all atoms. Protons have a positive charge and counteract the charge of electrons. The number of protons in the nucleus determines what the element is. For instance, atoms with one proton are the element hydrogen. Atoms with 8 protons are the element of Oxygen.

Neutrons are a subatomic particle of about the same mass as a proton but without an electric charge, present in all atomic nuclei except those of ordinary hydrogen.

Noble gasses are elements found in column 8 of the periodic table. Each element in this family (Helium, Neon, Argon, etc…) has a complete outer ring of electrons. All of their electrons are paired up. This is why noble gasses do not interact with other atoms.

An organic compound is any member of a large class of chemical compounds whose molecules contain carbon and hydrogen

Reactions: The nucleus of is never changed or altered after a chemical reaction. For instance, 2H2O can be broken back down to 2H2 and O2.

Solute – this is the substance that gets dissolved. For example, lemonade drink mix is the solute that gets added to the water (solvent).

Solvent – the substance the does the dissolving. For example, water is the solvent when you mix in lemonade drink mix.

Solution: a substance consisting of two or more substances mixed together and uniformly dispersed, most commonly the result of dissolving a solid, fluid, or gas in a liquid. A solution is a homogeneous mixture of two or more substances. Hydrogen Peroxide when mixed with water is a solution. Air is a solution. An example of a liquid solution is aqueous hydrochloric acid (HCl in water). A solution may exist in any phase. An example of a solid solution is brass. Glass is another solid solution.

Subatomic Particles = particles smaller than an atom. Protons, neutrons and electrons are subatomic particles. In other words, they are particles that are smaller than the atom.

A suspension is a heterogeneous mixture of larger visible particles that will settle out over time. Muddy water is a suspension.

Symbol: Elements have been given a symbol. The symbol consists of one, two or three letters. If there is more than one letter for the symbol, only the first letter is capitalized. The symbols for some elements have been known since ancient times and are derived from their Latin names. Ex: Potassium (K) is Kalium in Latin. Sodium (Na) is Natrium in Latin.

Valence electrons are electrons outside filled rings or shells. They are the outer electrons.

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