Matter & The Atom (adapted from a ppt on

Matter The term matter describes all of the physical substances around us. Matter is anything that has mass and takes up space. The Universe is made up of matter and energy.

Measurement of Matter Mass is a measurement of the amount of matter in an object. –Units are grams of any size. mg, kg, cg, g Volume is a measurement of the amount of space the object takes up. –Units of measure are liters or cubic centimeters. L, ml, dl, cc, cm 3

BIG IDEA….. All matter is made up of atoms. An atom is the smallest particle of matter that has characteristic properties.

Substances Substances that are made up of all the same type of particles are called pure substances. If all of the particles in that substance are the same type of atom, that substance is a particular kind of element.

Early Models of the Atom

Rutherford Mostly empty space Small, positive nucleus Contained protons Negative electrons scattered around the outside

Bohr Electrons move in definite orbits around the nucleus

Modern Model: The electron cloud Sometimes called the wave model Spherical cloud of varying density Varying density shows where an electron is more or less likely to be.

Atomic Structure Nucleus –Protons –Neutrons Orbitals or Shells –Electrons

Atomic Structure: Electron Tiny Have such a small mass that their mass is not included in the mass for that atom Have a negative electrical charge (-) Move around the outside of the nucleus in orbitals or electron shells Responsible for kinetic energy of atom

Atomic Structure: Proton Much larger than electrons Each proton has a mass equal to 1 Atomic Mass Unit (1 AMU) Protons have a positive charge (+) Located in the nucleus of the atom Responsible for the potential energy stored in the nucleus of the atom

Atomic Structure: Neutrons Large like protons Each neutron has a mass of 1 Atomic Mass Unit (1 AMU) Neutrons have no electrical charge Located in the nucleus of the atom Responsible for the potential energy stored in the nucleus of the atom

Atomic Structure

Determining Atomic Structure Atomic Number = number of protons In a neutral atom, the # of protons = the # of electrons Atomic Mass (AMU)= the sum of the number of protons and the number of neutrons

Alternate Forms of Atoms for the Same Element If the number of electrons change but the number of protons stay the same, the particle is called an ion. If the number of neutrons change but the number of protons stay the same, the particle is called an isotope.

Ions An atom with an electrical charge When an electron moves away from a neutral atom, that atom becomes a positively charged ion. If an electron joins a neutral atom, that atom becomes a negatively charge ion.

Ions The number of protons does not change in an ion. The number of neutrons does not change in an ion. So, both the atomic number and the atomic mass remain the same. Only the charge is changed.

Ions This atom has lost an electron. Now it has one more proton than electron. One more proton means one more positive charge. This makes the total charge of the atom POSITIVE. This atom has gained an electron. Now it has one less proton than electron. One less proton means one less positive charge. This makes the total charge of the atom NEGATIVE.

Examples of Common Ions When sodium chloride (table salt) is dissolved in water, the atoms in the molecule separate. The sodium atom loses an electron and the chlorine atom gains it. Sodium is then a positively charged ion. Chlorine is then a negatively charged ion.

Isotopes An atom with more or less neutrons than the most common form for that element is called an isotope. Two atoms of the same element with different numbers of neutrons are called isotopes. Isotopes have the same atomic #. Isotopes have different atomic masses.

Isotopes

Examples of Isotopes Common isotopes are frequently given special names. Hydrogen with one proton, one electron and two neutrons is a hydrogen isotope or deuterium. Carbon with six protons, six electrons and 8 neutrons is Carbon 14 (C-14).

Stay tuned for ppt on molecules…..