Atomic Structure Flashcards
What did daltons theory say about the structure of an atom
- All elements are made up of small invisible particles called atoms
- Atoms cannot be created or destroyed
- Atoms of different elements have different properties
- When atoms combine they form molecules or compounds
What did J.J. Thompson model of an atom look like
Plum pudding
Who discovered the electron
J J Thompson
Relative mass of proton
1
Relative mass of neutron
1
Relative mass of electron
1/1840
Relative charge of proton
+1
Relative charge of neutron
0
Relative charge of electron
-1
How to remember the relative charges
Neutrons= neutral
Protons= positive
Electrons= negative
Where are the protons and neutrons
Nucleus
Where are the electrons
In shells orbiting the nucleus
The shells can be filled by 2,8,8,8
What is an atom composed of
An atom is composed of a small dense positively charged nucleus at the centre composed of protons and neutrons (most of the mass) with negatively charged electrons in shells orbiting the nucleus.
Radius of an atom
0.1nm
What’s the atomic number
The number of protons in the nucleus of an atom
What’s the mass number
Total number of protons and neutrons in the nucleus of an atom
How do the atoms of one element differ to the atoms of another
The n.o. of protons, neutrons and electrons found in each atom are different
What is an element
A substance that consists of only one type of atom and it cannot be broken down into anything simpler by chemical means.
What’s the top number
Mass number
What’s the bottom number
Atomic number
How to find number of neutrons
Mass - atomic number
(Top - bottom)
The number of protons is equal to
The atomic number
Also the number of electrons
Where do the electrons go first
In the shell closest to the nucleus first.
Each shell must be filled with its full quota before starting to fill the next.
First has 2
The rest have 8
Ions
Atoms with electric charges
Cations
Atoms with positive charges (loss of electron/s)
Anions
Atoms with negative charges (gain of electron/s)
Difference between cation and anion
Cation = positive ion
Anion = negative ion
What makes something stable
Filled outer shells. Noble gases have full outer shells making them very stable.
How can you make something more stable
Adding or losing an electron/s.
When they gain/lose electrons they form ions
What would it mean if it said Ca 2+
Calcium has lost 2 electrons in its outer shell
What would it mean if it said Na +
Sodium has lost one electron
What would it mean if it said Cl -
Chlorine has gained one electron and became a chloride ion
What are isotopes
Isotopes are atoms which have the same number of protons (so they are atoms of the same element) but they have a different number of neutrons (so they have a different mass number)
This isn’t a question just an example
This is an example of a common isotope of chlorine
Chlorine 35 p=17 e=17 n=18. Chlorine 37 p=17 e=17 n=20
What are the most common mass numbers of chlorine
Also how do you find the relative mass
75% of chlorine atoms have a mass of 35.
25% of chlorine atoms have a mass of 37.
This is to calculate the relative mass of chlorine from the mass number and abundances if it’s isotopes: Average mass number = (75x35) + (25x37) divide by 100
= 35.5
Calculate the relative atomic mass of boron when it contains…
19.77% 10B , 80.23% 11B
Method: (19.77x10)(80.23x11) divide by 100
=10.8
Calculate the relative atomic mass of silicon when it contains ….
92.18% 28Si, 4.70% 29Si, 3.12% 30Si
Method: (92.18x28)(4.70x29)(3.12x30) divide by 100
=28.1
How do you identify isotopes
The protons and electrons of different atoms are the same but they have a different number of electrons
How to identify which elements are isotopes for each other
The bottom (atomic) number will be the same but the top (mass) number will be different
How is the periodic table arranged
In order of atomic numbers
Fill in this sentence…
For every element _________ number is unique
For every element atomic number is unique
How many electrons can the first shell hold
2
How many electrons does helium have
2
As we go across the rows in the periodic table what happens to the second electron shell?
The outer shells gain an extra electron
What particle in the atom did Chadwick discover
Neutron
What did JJThompson do
Plum pudding model, stated negative electrons embedded in a positive sphere
What did Rutherford do?
Model had negative electrons orbiting a positive nucleus
