1.
2.
3.
4.
1. the number of electrons
2. the chemical nature of the atom
3. its atomic number
4. its atomic weight
its atomic weight
1. 140
2. 144
3. 142
4. 146
144
1. proton
2. neutron
3. electron
4. alpha- particle
electron
1. neutron
2. α-particle
3. deutron
4. electron
neutron
1. 40 days
2. 20 days
3. 1.25 days
4. 30 days
30 days
1. 18270 years
2. 11520 years
3. 17280 years
4. 5760 years
11520 years
1. two positions on left
2. one position on left
3. one position on right
4. two positions on right
two positions on left
1. lead is stable
2. lead has high atomic mass
3. lead is a poor conductor
4. lead is a good absorber
lead is a good absorber
1. 3015P
2. 3014Si
3. 157N
4. 2411Na
3015P