2.1 The Nature of Matter
Basic unit of matter May be broken into smaller particles that do NOT have the properties of the element.
Very small- 100 million atoms would make a row only about 1 centimeter long Consists of protons, neutrons, and electrons.
Nucleus Core of atom Protons Positive charge, in nucleus, mass of 1 atomic unit Neutrons No charge, in nucleus, mass of 1 atomic unit Electrons Negative charge, orbits nucleus, mass of 0 atomic units (technically a mass of 1/1840).
Atoms have equal numbers of electrons and protons, their positive and negative charges balance out, and atoms themselves are electrically neutral.
Matter is made up of atoms Atoms join together to make compounds Compounds use chemical bonds to hold them together Chemical bonds are stored energy Molecule Atoms of the same element joined together.
Elements and isotopes have same number of electrons All isotopes of an element have the same chemical properties.
Pure substance that consists entirely of one type of atom or Elements cannot be broken down into other types of substances Mercury (Hg).
Atoms of the same element that differ in the number of neutrons.
Atomic number Number of protons Atomic Number (atomic mass or weight) Number of protons and neutrons.
Atomic Number 6 Mass Number 12
Nuclei are unstable and break down at a constant rate over time Used for Determine the ages of rocks and fossils by analyzing the isotopes found in them Detect and treat cancer Kill bacteria that cause food to spoil Labels or “tracers” to follow the movements of substances within organisms.
Substance formed by the chemical combination of two or more elements in definite proportions Water, the chemical formula H 2 O, contains two atoms of hydrogen for each atom of oxygen.
Physical and chemical properties of a compound can be different from the elements that forms it Sodium Reacts explosively with cold water Chlorine Very reactive, poisonous, greenish gas that was used in battles during World War I Sodium Chloride Table salt.
Attraction between two atoms resulting in a sharing or transferring of an electron(s) Uses electrons Covalent Bond Chemical bond that SHARES electrons Ionic Bond Chemical bond that TRANSFERS electrons Hydrogen Bond Weak bond between hydrogen ions.
Transfer of electron(s) Ion A charged particle Protons do NOT equal electrons
A sodium atom easily loses its one valence electron and becomes a sodium ion (Na + ).
A chlorine atom easily gains an electron (from sodium) and becomes a chloride ion (Cl ).
Slight attraction can develop between the oppositely charged regions of nearby molecules Due to unequal sharing of electrons within each molecule Much weaker than Covalent of Ionic bonds.