Atomic Structure and the Periodic Table
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What determines the size of an atom?
Volume of electron’s orbits
What is radius of an atom?
0.1 nano meters
What is the charge of the nucleus and why?
Positive charge because protons
What does the nucleus contain?
Contains protons and neutrons
Where is almost the whole mass of atom is concentrated?
In nucleus
What is no. of protons equal to?
no. of electrons
What does the nuclear symbol of atom (i.e. what’s on the periodic table) tell you?
Its atomic number and mass number
What a mass number?
Total number of protons and neutrons in atom
What’s the atomic number?
Number of protons
How do find the no. of neutrons?
Mass Number − Atomic Number
What is the name given to substances that only contains atoms with same number of protons?
Elements
Define isotopes
Different forms of same element, which have same no. of protons, but different no. of neutrons
What is relative atomic mass?
Average mass of one atom of an element (including isotopes)
How are elements laid out in the periodic table?
In order of increasing atomic (proton) number
Where are metals & non-metals on the periodic table?
Metals are on left and non-metals on right
What does the group number tell you?
Number of electrons in outer shell Exception Group 0 which has Helium (2 electrons)
What do periods show you?
New period = another full shell of electrons
What does having one electron on the outer shell do to an atom?
Makes them very reactive and gives similar properties
Name 2 properties of Group 1 metals
All are soft and have low density
As you go down Group 1…. (Name 3 things)
• Increasing reactivity • Lower melting points • Lower boiling points (4. Higher relative atomic mass)
Why does reactivity increase as you go down Group 1?
• Outer shell electron is further away from nucleus, further down the group • ∴ attraction between nucleus and electron decreases • Outer electron is more easily lost
What do alkali metals form with non-metals & why?
Ionic compounds with charge go +1 - don’t need much energy to remove 1 outer electron to form full outer shell
What are ionic compounds formed from alkali metals and non-metals like?
Usually white solids that dissolve in water to form colourless solutions
Name 3 observations that occur when alkali metals react with water
• Metal travel quickly along surface of water • Lots of fizzing • Metal gets smaller • Universal indicator turns purple