Understanding the Periodic Table ARRANGEMENT OF PERIODIC TABLE
Understanding the Periodic Table
ARRANGEMENT OF PERIODIC TABLE • Mendeleev arranged elements by increasing atomic number
Subatomic particles • Protons- positive charge - nucleus • Neutrons- neutral (no) charge - nucleus • Electrons- negative charge – outside the nucleus
Atomic Number • Number assigned to element that appears above the symbol 5 B Boron 10. 81 • Atomic number = protons = electrons
Atomic Mass • Also referred to as atomic weight or (amu) atomic mass unit 5 B Boron 10. 81 Atomic mass (rounded off) – atomic number = neutrons
Chemical Symbol • A capital letter or a capital letter and one lower case letter • NEVER TWO CAPITAL LETTERS FOR ONE ELEMENT
Let’s practice what we know so far Element Nitrogen Carbon Neon Symbol Atomic # Protons Neutrons Electrons
Groups or Families • Vertical columns on the periodic table • There are 18 of them • Each family has a family name
Periods • Horizontal rows on the periodic table • There are 7 of these
Other things we can tell about the element… • Remember the 7 periods? – The period tells us how many rings (shells, orbits, clouds or energy levels) the element has • Argon is in period 3, so it will have 3 rings
Remember the group number? • There are 18 groups (families) and if you look at the group number…the ones column of the group number…that will tell you the number of valence electrons the atom will have! Atoms in group 14 will have 4 valence electrons. Family 2 has 2.
Valence Electrons • These are the electrons found on the outermost shell
Now let’s look at the electrons… Element Oxygen Symbol O Atomic # Protons 8 Element Oxygen Neutrons 8 8 Period 2 Electrons 8 Family/gro up 16
What is this? You will need this. Shell K L M N O P Q # of electrons 2 8 8 or 18 8 or 32 8 or 18 8 2 The sure-proof guide to Electron Distribution 1. The number of electrons is equal to the number of protons (atomic number) 2. The number of orbits (shells) is equal to the period number of the elements 3. The number of electrons in an element’s outer orbit (valence) (this is to be filled first) is equal to its group number (ones column only) 4. Then fill from “K” shell to the outside. Your inner shell must be filled (complete) before you move on to the next shell
More about electrons… • Why do atoms combine? To Be “Happy” AKA “Stable” • The “law” of Electrons All atoms want to have eight electrons in their outer energy level, unless that energy level is the “K” or “Q” energy level, then they want two
Bohr model Element Oxygen Period 2 # of shells Family/group 16 # of valence electrons We know that Oxygen has 8 electrons. It will have 2 shells since it is in period 2. It will have 6 outermost electrons. We look at the group/family number (the ones column only)
Let’s do one…
One more…
Lewis Dot Diagram • Use the symbol of the element and the number of valence electrons and place a dot to represent the number of valence electrons with a dot. • Begin to the right of the symbol and go counter clockwise. • There will never be more than 8 dots since there will never be more than 8 valence electrons. Al 2 3 1
Now you try… Ge
What did we learn? • • The arrangement of the periodic table What subatomic particles are How to read the periodic table What valence electrons are How to create Bohr Models Family Names of the periodic table How to create a Lewis Dot Diagram
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