Transcript ATOMS
ATOMS • The smallest particle of an element that has properties of that element is called the ATOM. It is the BASIC BUILDING BLOCK OF ALL MATTER. • An atom that has no charge; it’s neither positive or negative is called a NEUTRAL ATOM. • The atom is made up of 3 parts or subatomic particles. They are the PROTON, ELECTRON, and NEUTRON. • The PROTON has a positive charge (+), is found in the NUCLEUS, and has a mass of 1. • The NEUTRON is neutral, is found in the NUCLEUS, and has a mass of 1. • The ELECTRON has a negative charge (-), moves around the nucleus, and has a mass of 0. • The NUCLEUS is the positively charged center of an atom. Since atoms are neutral, the protons need to balance electrons. Therefore, the number of protons = the number of electrons (p’s = e’s) • Atoms and Bonding Video (1:40) The Structure and Scale of Atoms Video (2:46) • The ATOMIC NUMBER is the number of protons in the nucleus of an atom. For example: Carbon’s atomic number is 6. So, there are 6 protons in the nucleus. Oxygen has an atomic number of 8. • How many protons are there? • 8 • How many electrons are there? • 8 • The MASS NUMBER or ATOMIC MASS is the sum of the number of protons and number of neutrons. • #p + #n = mass # • #n = mass # - atomic # • Because atoms are soo small, we are unable to see them. Therefore, scientists make and use MODELS to represent them. There are 2 models for atoms. BOHR MODEL • Claimed that electrons moving around the nucleus only travel in orbits like planets thus it was called a PLANETARY MODEL • Bohr’s model of the atom video (00:52) ELECTRON CLOUD MODEL • This is the current model we use today & is more accurate. It says that electrons are found in a “cloud” around the nucleus (kind of like the spray of water from a sprinkler, each drop represents where an electron might be). • Electron Cloud Model Video (00:33) ATOMS COMBINE • Most matter is in the form of COMPOUNDS or mixtures of compounds. For example: salt (NaCl), water (H20), carbon dioxide (CO2) • Compounds have properties UNLIKE those of their elements. For example: Salt—Sodium (Na) is a shiny, soft, gray, explosive metal with water & Chlorine (Cl) is a yellowish-green gas that can kill but when they combine, it forms sodium chloride or table salt. • A CHEMICAL FORMULA tells what elements make up a compound & the ratios of the atoms to those elements. • For example: NaCl (salt) means there is 1 atom of sodium (Na) to every 1 atom of chlorine (Cl). • A SUBSCRIPT is a number in a chemical formula written after a chemical symbol that tells how many atoms of an element there are in the compound. It means “written below”. • For example: H20 (2 is the subscript) There are 2 atoms of hydrogen (H) and 1 atom of oxygen (O). This makes up 1 molecule of water. Video on Compounds (3:59) • A CHEMICAL BOND is a force that holds atoms together in a compound. They use electrons to bond. There are 2 types of bonds. 1. IONIC BOND • The transfer of electrons from one element to another. • It is made of charged particles (+ and – atoms). • Example: Na(+)Cl (-) = ionic bond/compound Ionic Bonding video (2:18) 2. COVALENT BOND • • • • The sharing of electrons between elements. It is NOT made of charged particles. Example: H2O = covalent compound Covalent Bonds Video (1:23) Covalent Bonds video (1:23) PHYSICAL CHANGES • ANY CHANGE IN MATTER THAT DOES NOT CHANGE THE IDENTITY OF THE MATTER • EXAMPLES: CUTTING, GRINDING, CHANGING THE STATE (MELTING, FREEZING, ETC.) CHEMICAL CHANGES • CHANGE IN MATTER IN WHICH ONE SUBSTANCE IS CHANGED INTO ANOTHER SUBSTANCE. • EXAMPLES: BURNING, RUSTING • Chemical Changes vs. Physical Changes Video (1:52) Chemical Changes vs. Physical Changes video (1:52) EVIDENCE OF A CHEMICAL CHANGE/REACTION: • • • • COLOR CHANGE PRECIPITATE FORMED HEAT PRODUCED OR REQUIRED GAS GIVEN OFF • Evidence of Reactions Video (2:44) Evidence of Reactions video (2:44)