Atomic Structure & Periodic Table

Atoms The smallest part of an element any smaller and it is no longer that element! There is a different atom for each element. The number of protons determine the element. 3 protons = Lithium 20 protons = Calcium IF an atom has no charge, then the number of protons (positive charges) equals the number of electrons (negative charges).

Protons Have a positive charge Equals the atomic number Equals the number of electrons, if the atom has no charge Determines the type of element Lives in the nucleus with neutrons

Neutrons Have no charge Have mass. So you compute neutrons by atomic mass – atomic number (protons) Live in the nucleus with the protons Can vary without changing the type of element

Electrons Have a negative charge Can give you the identify of the element IF the atom has no charge Has almost no mass Can vary without changing the type of element

Atomic Number Located above the element’s symbol Always tells the number of protons and sometimes the number of electrons IF the atom is neutral (no charge)

Atomic mass The number of protons plus neutrons in an atom. Almost all of the mass is located in the nucleus because electrons have such little mass. Is often indicated by the name of the element followed by the mass. Example Lithium – 7 Can vary without changing the type of element

Periodic Table

Arranged by Increasing atomic number (protons) Why isn’t it arranged by increasing atomic mass?

Periods Rows Indicate the number of electron clouds each atom of that element has NOT ALWAYS THE SAME STATE OF MATTER AT ROOM TEMPERATURE

Families or groups Columns All have the same number of electrons in their valence (same number of valence electrons) All react similarly and have similar physical and chemical characteristics NOT ALWAYS THE SAME STATE OF MATTER AT ROOM TEMPERATURE

Metals left of the “zig zag”/staircase. Metals are: shiny, ductile, malleable, thermally and electrically conductive MOST but not all are solids

Nonmetals Located to the right of the “zig zag” or staircase MOST are gasses at room temperature. Characteristics of nonmetals include: dull, brittle when they’re a solid and not good conductors of thermal or electrical energy

Metalloids Located on the zig zag line. Have characteristics of BOTH metals and nonmetals in each

Reactivity The elements on the left of the periodic table are more reactive then the ones to their right. As you move from left to right, reactivity decreases

Hydrogen Reacts like a metal but has the characteristics of nonmetals. The most abundant element in the universe

Describe an atom Using potassium, describe the atom using the following words: Proton, neutron, electron, electron clouds, nucleus