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Chemistry Vocabulary
8th Grade Science Unit 1
Term | Definition |
---|---|
atom | The smallest particle of an element that cannot be broken down without losing its properties; basic unit that makes up all matter. |
atomic mass | The average mass of an atom. (protons + neutrons) |
atomic number | The number of protons found in the nucleus of an atom. |
Bohr model | Simple model of an atom that shows the distribution of protons and neutrons in the nucleus and the distribution of electrons in orbiting energy levels. |
chemical bond | The force that holds the atoms of molecules and compounds together. |
chemical change | Change in a substance through chemical reactions to form new substances with different properties. |
chemical equation | A short simple way to describe a chemical reaction using symbols. |
chemical reaction | When chemical bonds are broken and atoms rearrange, a chemical reaction occurs. |
coefficient | The number of each molecule in a chemical formula. |
compound | A substance made up of two or more different types of atoms (elements). |
conductor | Materials that readily conduct an electric current. |
conservation of mass | States that mass cannot be lost or gained. Therefore, the number of atoms and mass at the beginning of a reaction must equal the number or atoms and mass at the end of a reaction. |
electron | A subatomic particle, with a negative charge, found outside the nucleus of an atom. |
electron cloud | The area surrounding the nucleus of an atom where electrons can be found. |
element | The simplest form of a molecule made of only one type of atom with a certain number of protons and properties unique to that element. |
energy level/shell | Refers to the electron configuration outside the nucleus of an atom. |
group /Family | Numbered columns of the periodic table. Numbers correlate with the number of valence electrons for a neutral atom. |
halogen | Highly reactive elements found in group 17 of the periodic table with 7 valence electrons. |
malleable | Physical property of metals and metalloids. Malleable metals can easily be deformed, especially by hammering or rolling, without cracking. |
mass number | The number of protons and neutrons in an element. It is equal to the atomic mass rounded to the nearest whole number. (#protons + #neutrons) |
metal | Elements located to the left of the zigzag line on the periodic table. Generally, these are good conductors, reactive and have shiny luster. |
metalloid | Elements found along the zig-zag of the periodic table that share properties of both metals and non-metals. |
molecule | Two or more atoms of same or different kinds chemically bonded together. |
noble gas | Elements found in group 18 of the periodic table. These elements generally do not form compounds with other elements because their outer energy level is full. |
non-metal | Elements located to the right of the zigzag line on the periodic table. These are generally poor conductors. |
nucleus | The dense center of an atom containing the protons and neutrons. |
neutron | A subatomic particle with no charge (neutral) found in the nucleus of an atom. |
organic compound | Any compound that contains Carbon (C). |
periods | The numbered rows of the periodic table. Numbers indicate the number energy levels (shells) for an atom. |
physical change | A change in a substance that does not involve a chemical reaction, so no new substance is formed. |
precipitate | The formation of a solid in a solution during a chemical reaction. |
product | The resulting substances in a chemical reaction found to the right of the yield sign. |
proton | A positively charged subatomic particle that determines an element’s identity. |
reactant | Any substance present initially in a chemical reaction found to the left of the yield sign. |
subatomic particle | Particles smaller than an atom that combine to form an atom. |
subscript | The number of atoms of an element in a molecule. |
valence electron | Electrons in the outermost energy level of an atom. |
yield sign | The symbol in a chemical equation that indicates the direction of the reaction. Shown with an arrow. |