ATOMS

What is an atom? Atoms are the fundamental building blocks of all things Atoms are the most basic unit of matter

Atoms are made up of protons, neutrons, and electrons Protons: particles with a positive charge; can be found in the nucleus Neutrons: particles with no charge (a neutral charge); can be found in the nucleus Electrons: particles with a negative charge that can be found orbiting the nucleus in the electron cloud

The atomic number equals the number of protons. The electrons in a neutral atom equal the number of protons. The mass number equals the sum of the protons and neutrons.

Where are electrons found? Electrons exist in orbitals or energy levels 2 electrons fit in the first energy level 8 electrons fit in each subsequent energy level Carbon (C) Helium (He) 6 neutrons 6 protons 6 electrons 2 in first level, 4 in second 2 neutrons 2 protons 2 electrons

The charge indicates the number of electrons that have been lost or gained. A positive charge indicates the number of electrons (which are negatively charged) that have been lost. A negative charge indicates the number of electrons that have been gained. This structure can be written as part of a chemical symbol.

Check for Understanding With your partner, answer the following question: If an element has a NEGATIVE charge, has it lost or gained electrons? Time: 30 seconds

A chemical element is a pure substance that consists entirely of one type of atom. Elements are mapped on the periodic table.

Do all atoms of the same element always have the same number of neutrons? Answer: NO Atoms of the same element with differing numbers of neutrons are called isotopes

The combinations of two or more elements in definite proportions form a chemical compound. Naming compounds (molecular formulae): H20 = 2 parts hydrogen to 1 part oxygen

Compounds and their properties The physical and chemical properties of a compound are usually very different from those of the elements from which it is formed. Example: Sodium is a silverish metal Chlorine is a greenish gas Sodium Chloride (NaCl) is table salt

Impress Ms. Moloney Can you and your partner come up with one other compound whose properties are very different from the properties of the individual elements that make up the compound?? Hopefully most of them come up with H2O…..give hints if they are stuck. “You use it everyday” “Your body needs it to survive”

How atoms in compounds are brought together Ionic bonds are formed when one or more electrons are transferred from one atom to another Example: Sodium Chloride (NaCl)

How atoms in compounds are brought together Covalent bonds are formed when electrons are shared between atoms A molecule is the structure that results when atoms join together by covalent bonding Example: H2O (Water) HCl (Hydrogen Chloride) CO2 (Carbon Dioxide) For their notes, tell them to simply write that in ionic bonds electrons are transferred, in covalent they are shared

Van der Waals Forces When molecules are close together, the oppositely charged regions are attracted to each other. Van der Waals Forces are the slight forces of attraction These forces explain why a gecko can climb up vertical surfaces (suction cup like forces)