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Transcript
Atoms and the Periodic Table Atom The smallest unit of an element Atoms are made of even smaller subatomic particles: protons, neutrons, and electrons. Protons carry a positive charge, electrons carry a negative charge and neutrons are neutral! Charges An atom is neutral when the number of protons is equal to the number of electrons. An ion is a charged atom! A positively charged atom is called a Cation – it has more protons than electrons A negatively charged atom is called an Anion – it has more electrons than protons. Periods Periods go left to right. There are 7 periods in total. Elements have something in common if they are in the same period. All of the elements in a period have the same number of atomic orbital's. Every element in the top row (the first period) has one orbital for its electrons. Hydrogen is from period 1 and has one orbital. Potassium is from period 4 and has 4 orbital's. Groups These are the vertical columns on a periodic table. There are 18 columns which are called groups or families. Excluding the transition metals, each element in a group has the same number of electrons in the outer shell. Families Elements in the same family have similar properties, some examples are: EXAMPLES OF PHYSICAL PROPERTIES - Density - Boiling Point - Melting Heat Capacity -State of matter at room temperature EXAMPLES OF CHEMICAL PROPERTIES - Combustibility - Reactivity - Radioactivity EXAMPLES OF FAMILIES - Alkali Metals - Alkaline Earth Metals - Transition Metals - Basic metals - Metalloid - Non Metals - Halogen Gases - Noble Gases - Lanthanide Series - Actinide Series Reading the Periodic Table Atomic Number The number of protons in an atom identifies the element and the atomic number . Atomic Symbol: The atomic symbol is one or two letters chosen to represent an element ("H" for "hydrogen," etc.). Reading the Periodic Table Atomic Mass The atomic mass is the average mass of an element in atomic mass units ("amu"). To calculate the mass you add the total protons and neutrons. Electrons have such little mass that they are not even factored in the equation.