Chapter 8.1: Electrons and Energy Levels


Published on

8th Grade Integrated Science Chapter 8 Lesson 1 on Electrons and Energy Levels. This lesson gives a brief introduction of the periodic table, periods, and groups. There is an introduction to metals, nonmetal, and metalloids. This also introduces electrons, energy levels, and the basic idea of bonding.

Published in: Education, Technology, Business
  • Be the first to comment

No Downloads
Total views
On SlideShare
From Embeds
Number of Embeds
Embeds 0
No embeds

No notes for slide

Chapter 8.1: Electrons and Energy Levels

  1. 1. Chapter 8.1 Electrons and Energy Levels
  2. 2. Periodic Table • Shows: – Elements – Atomic Number – State of matter at room temperature – Atomic (average) Mass
  3. 3. Periods and Groups • • • • Period = Rows Groups = Columns Lists elements in order of atomic number Atomic number increases as you move from left to right • Elements in each group have similar chemical properties and react with other elements in similar ways
  4. 4. Metals, Nonmetals, and Metalloids • Metals – Often shiny – good conductors of electricity and thermal energy – Easily pulled into wires and hammered into sheets • Metalloids – Have properties in common with both metals and nonmetals – Often used as semiconductors in electronic devices • Nonmetals – Poor conductors of thermal energy and electricity – Most are gases at room temperature – Solid form tends to be brittle
  5. 5. Atoms Bonds • Pure elements are rare to find • Atoms of different elements chemically combine and form compounds. • Compounds make up all living and nonliving things • Chemical bonds hold together different elements in chemical compounds • A chemical bond is a force that holds two or more atoms together
  6. 6. Electron Number and Arrangement • The exact position of electrons in an atom cannot be determined. • Electrons are in constant motion around the nucleus • However, each electron is usually in a certain area of space around the nucleus • Some are in areas close to the nucleus, and some are in areas farther away
  7. 7. Electrons and Energy • Different electrons in an atom have different amounts of energy. • An electron moves around the nucleus at a distance that corresponds to its amount of energy • Areas of space in which electrons move around the nucleus are called energy levels • Electrons closet to the nucleus have the least amount of energy – They are at the lowest energy level – Only 2 electrons can be in the lowest energy level
  8. 8. Electrons and Bonding • Negatively charged electrons have a similar attraction to the positively charged nucleus of an atom (like a magnet) • The electrons in the energy levels closest to the nucleus of the same atom have a strong attraction to that nucleus • Electrons farther from that nucleus are weakly attracted to it. – These outermost electrons can easily be attracted to the nucleus of the other atoms • This attraction between the positive nucleus of one atom and the negative electrons of another is what causes a chemical bond.
  9. 9. Valence Electrons • Electrons farthest from their nucleus are easily attracted to the nuclei of nearby atoms. • These outermost electrons are the only electrons that can form chemical bonds – This is because these electrons are exposed to the nuclei of other atoms • A valence electron is an outermost electron of an atom that participated in chemical bonding. • Valence electrons have the most energy of all electrons in an atom.
  10. 10. Valence Electrons • The number of valence electrons in each atom of an element can help determine the type and the number of bonds it can form. • The periodic table can tell you how many valence electrons an atom has. • Except for Helium, elements in certain groups have the same number of valence electrons • In groups 1,2, 13-18, the number of valence electrons is shown by the ones digits of the group. – So, elements in group 18 have 8 valence electrons.
  11. 11. Electron Dot Diagrams • In 1916, an America Chemist named Gilbert Lewis developed the electron dot diagram. • The electron dot diagram is a model that represents valence electrons in an atom as dots around the element’s chemical symbol • It can help you predict how an atom will bond with other atoms • The dots represent the valence electron • Some dots pair up, others do not • The number of unpaired dots is often the number of bonds an atom can form • See Figure 5, pg 271
  12. 12. Valence Electrons • Remember that each element in a group has the same number of valence electrons. • SO, every element in a group has the same number of dots in its electron dot diagram • Atoms with 8 valence electrons do not easily react with other atoms – They are chemically stable • Atoms that have 1-7 valence electrons are reactive of chemically unstable – They easily bond with other atoms and form chemically stable compounds • Atoms of H and He have only one energy level – These atoms are chemically stable with two valence electrons
  13. 13. Noble Gases • Elements in Group 18 are called noble gases • With the exception of He, noble gases have eight valence electrons and are chemically stable. • Chemically stable atoms do not easily react, or form bonds, with other atoms
  14. 14. Stable and Unstable Atoms • Atoms with unpaired dots in their electron dot diagram are reactive, or chemically unstable. • For example, N has 5 valence electrons are 3 of them are unpaired. – It is reactive and will become more stable by forming chemical bonds with other atoms • When an atom forms a bond, it gains, loses, or shares valence electrons with other atoms. • By forming bonds, atoms become more chemically stable