Question

what is the mass number of first 20 elements in the periodic table

Answer 1

 

Atomic
Weight

Name

Sym.

M.P.
(°C)

 B.P.
 (°C)

Density*
(g/cm3)

Earth
crust (%)*

Discovery
(Year)

Group*

Electron
configuration

Ionization
energy (eV)

1

1.008

Hydrogen

H

-259

-253

0.09

0.14

1776

1

1s1

13.60

2

4.003

Helium

He

-272

-269

0.18

1895

18

1s2

24.59

3

6.941

Lithium

Li

180

1,347

0.53

1817

1

[He] 2s1

5.39

4

9.012

Beryllium

Be

1,278

2,970

1.85

1797

2

[He] 2s2

9.32

5

10.811

Boron

B

2,300

2,550

2.34

1808

13

[He] 2s2 2p1

8.30

6

12.011

Carbon

C

3,500

4,827

2.26

0.09

ancient

14

[He] 2s2 2p2

11.26

7

14.007

Nitrogen

N

-210

-196

1.25

1772

15

[He] 2s2 2p3

14.53

8

15.999

Oxygen

O

-218

-183

1.43

46.71

1774

16

[He] 2s2 2p4

13.62

9

18.998

Fluorine

F

-220

-188

1.70

0.03

1886

17

[He] 2s2 2p5

17.42

10

20.180

Neon

Ne

-249

-246

0.90

1898

18

[He] 2s2 2p6

21.56

11

22.990

Sodium

Na

98

883

0.97

2.75

1807

1

[Ne] 3s1

5.14

12

24.305

Magnesium

Mg

639

1,090

1.74

2.08

1755

2

[Ne] 3s2

7.65

13

26.982

Aluminum

Al

660

2,467

2.70

8.07

1825

13

[Ne] 3s2 3p1

5.99

14

28.086

Silicon

Si

1,410

2,355

2.33

27.69

1824

14

[Ne] 3s2 3p2

8.15

15

30.974

Phosphorus

P

44

280

1.82

0.13

1669

15

[Ne] 3s2 3p3

10.49

16

32.065

Sulfur

S

113

445

2.07

0.05

ancient

16

[Ne] 3s2 3p4

10.36

17

35.453

Chlorine

Cl

-101

-35

3.21

0.05

1774

17

[Ne] 3s2 3p5

12.97

18

39.948

Argon

Ar

-189

-186

1.78

1894

18

[Ne] 3s2 3p6

15.76

19

39.098

Potassium

K

64

774

0.86

2.58

1807

1

[Ar] 4s1

4.34

20

40.078

Calcium

Answer 2

1)2
2)4
3)5
4)7
5)10
6)12
7)14
8)16
9)18
10)21
11)23
12)24
13)27
14)28
15)31
16)32
17)35.5
18)40
19)39
20)40