Atoms and molecules
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Atoms and Molecules. Protons, Neutrons and Electrons. Orbiting the nucleus. nucleus. nucleus. +1. neutral. -1. Can vary. Same as electrons. Same as protons. Determines atomic number. Proton. Neutron. Electron. What’s wrong with this atom?. Proton. Too many neutrons

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Protons neutrons and electrons
Protons, Neutrons and Electrons

Orbiting the nucleus






Can vary

Same as electrons

Same as protons

Determines atomic number




What s wrong with this atom
What’s wrong with this atom?


Too many neutrons

# of particles in nucleus is the same as the electron #

Too many electrons

Too many protons



What element is this
What element is this?





Not enough information to determine



What element is this1
What element is this?





  • The atomic number tells you the number of protons in the nucleus

  • Each type of atom has a different atomic number and is a different element

  • As of 2011, there are 118 elements.

  • While the proton # determines the element, each element can have varying #’s of neutrons. These are called isotopes

Chemical bonds
Chemical Bonds

  • Electrons are organized into layers called shells surrounding the nucleus

  • The first shell can hold 2 electrons, the second shell can hold 8, and all additional shells can hold 8 electrons in the outer shell

  • Atoms that have 8 electrons in their outer shell are stable and normally do not form bonds

  • Atoms that do not have 8 electrons in their outer shell will form chemical bonds with other atoms to fill their outer shell and become stable

Ionic bonds
Ionic Bonds

  • An atom may steal an electron from another to fill its outer shell.

  • The atom that loses the electron also ends up with a full outer shell

  • The atom that stole the electon now has more electrons than protons and becomes a negatively charged ion

  • The atom that lost the electron now has more protons than electrons and becomes a positively charged ion

  • Both atoms are attracted and bond to each other because of their opposite charges

Covalent bonds
Covalent Bonds

  • Two atoms may share electrons in their outer in order to fill their outer shell - remember: 2 electrons in the first shell and 8 in all others

Examples of covalent bonds
Examples of Covalent Bonds

Hydrogen now has a full outer shell: 2 electrons

Chlorine now has a full outer shell: 8 electrons

Water forms through covalent bonds
Water forms through covalent bonds

Oxygen has 6 electrons in its outer shell.

How many more does it need to be stable?

How many hydrogen atoms does oxygen need to share with to fill its outer shell?

Hydrogen has one electron in its outer shell.

How many more does it need to be stable?