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Model of Matter- Atoms and Molecules (What is an atom (Screen Shot 2018-09…
Model of Matter- Atoms and Molecules
What is an atom
An atom is the smallest possible unit of a substance that still has its chemical properties, and cannot be divided any further
Protons + Neutrons (In the nucleus)
Electrons (In electron shells)
Proton number = 3
Relative atomic mass (total number of protons+neutrons) = 7
Neutron number = 7-3 = 4
Proton number = 3
Electron number = 3 (the number of protons is the same as the number of neutrons since an atom has neutral charge)
Overall no charge
Electronic Structure
2•8•8 (Maximum Electronic Structure)
Elements in the same group number have the same number of valence electrons
Isotopes
Relative Atomic Mass
In order to calculate the relative atomic mass, we take an average of all the isotopes of the atom over the total
E.g.
Relative atomic mass of chlorine = (75)x35 + (25)x37 ➗100
= 35.5
Atoms chemically combine
To achieve the same stability as the noble gases with their stable electronic configuration
Gaining electrons
Tend to be non-metallic elements with more than 4 valence electrons
Become negatively charged ions, known as anions
X(m+) and Y(n-) = XnYm
Sharing electrons
When BOTH atoms need to gain electrons
Losing electrons
Tend to be metallic elements with less than 4 valence electrons
Become positively charged ions, known as cations
