Atomic Number 20

Posted on  by admin

The atomic mass of an element is the average mass of the atoms of an element measured in atomic mass unit (amu, also known as daltons, D). The atomic mass is a weighted average of all of the isotopes of that element, in which the mass of each isotope is multiplied by the abundance of that particular isotope. (Atomic mass is also referred to as atomic weight, but the term 'mass' is more accurate.)

In chemistry and atomic physics, an electron shell may be thought of as an orbit followed by electrons around an atom's nucleus.The closest shell to the nucleus is called the '1 shell' (also called the 'K shell'), followed by the '2 shell' (or 'L shell'), then the '3 shell' (or 'M shell'), and so on farther and farther from the nucleus.The shells correspond to the principal quantum numbers (n. Charles Hawkins HIS 991 atomic number 20 atomic number 20 n't you surmount some of your difficulty? 'The ambience became so strain that Chow was forced to break up the league.Chow dynasty subsequently called a serial publication of encounter, where it was agreed that the polyvinyl acetate would constitute divided into three grouping, to exist dispatched to Han-Gook in break; to. Calcium has an atomic number of 20 which means an atom of calcium has 20 protons and 20 electrons and a variable number of neutrons depending upon which isotope of Calcium it is. If an atom of an.

For instance, it can be determined experimentally that neon consists of three isotopes: neon-20 (with 10 protons and 10 neutrons in its nucleus) with a mass of 19.992 amu and an abundance of 90.48%, neon-21 (with 10 protons and 11 neutrons) with a mass of 20.994 amu and an abundance of 0.27%, and neon-22 (with 10 protons and 12 neutrons) with a mass of 21.991 amu and an abundance of 9.25%. The average atomic mass of neon is thus:

0.9048×19.992 amu=18.09 amu
0.0027×20.994 amu= 0.057 amu
0.0925×21.991 amu= 2.03 amu
20.18 amu

The atomic mass is useful in chemistry when it is paired with the mole concept: the atomic mass of an element, measured in amu, is the same as the mass in grams of one mole of an element. Thus, since the atomic mass of iron is 55.847 amu, one mole of iron atoms would weigh 55.847 grams. The same concept can be extended to ionic compounds and molecules. One formula unit of sodium chloride (NaCl) would weigh 58.44 amu (22.98977 amu for Na + 35.453 amu for Cl), so a mole of sodium chloride would weigh 58.44 grams. One molecule of water (H2O) would weigh 18.02 amu (2×1.00797 amu for H + 15.9994 amu for O), and a mole of water molecules would weigh 18.02 grams.

The original periodic table of the elements published by Dimitri Mendeleev in 1869 arranged the elements that were known at the time in order of increasing atomic weight, since this was prior to the discovery of the nucleus and the interior structure of the atom. The modern periodic table is arranged in order of increasing atomic number instead.

Atomic Number 20

Atomic Number Memory Pegs: 1-20

©John P. Pratt, all rights reserved
Icons drawn by David R. Pratt
16 September 1997Number

Using these Atomic Number Memory Pegs is described in theexplanation They are also arrangedin the shape of a traditional periodic tableas well as Pawlowski's new circular periodic table (described elsewhere).


1. Hydrant (Hydrogen H). Blue for 'first place' (blue ribbon) and for water, its principal compound; tall and thin, shaped like a '1'. Hydrant sounds like hydrogen (both refer to water).

2. Helium Balloon (Helium He). Silver colored for'second place' (silver medal); a noble color for a noble gas.

3. Lithium watch battery (Lithium Li), 3-volt. Lilac colored(sounds like lithium and all three natural minerals are lilaccolored).

4. Beryl-studded Belt Buckle (Beryllium Be). Rectangular (4 sides),with four pink beryls (beryl is a pink gem: beryllium aluminum silicate).

5. Box of Borax (Boron B). 5-pound box, dark brown, the color of pure boron(borax is hydrated sodium borate).

6. Charcoal pencil (Carbon C). Black, the color of charcoal and also of graphite (carbon) in pencil leads. Hexagonal (6-sided).

7. Dynamite, or Nitroglycerin (Nitrogen N). Two red sticks, shaped like a '7' (most explosives contain nitrogen).

8. Oxygen-filled Lifepreservers (Oxygen O). White for air,which preserves life. Two of them touching, shaped like an '8'.

9. Fluoride Toothpaste (Fluorine F). Purple, the color of the mineral fluorite (calcium fluoride), and shaped like a 9.

10. Neon Sign (Neon Ne). Shaped like a '10,' flashing orange,like the orange/red color of neon in neon signs.

11. Narrow Soda Crackers (Sodium Na). Two of them, brightyellow, shaped like an '11,' like the bright yellow sodium D spectrallines. Sodium is named for soda (sodium carbonate).

12. Mug. (Magnesium Mg) 12 oz. green mug made of olivine(magnesium silicate), filledwith milk of magnesia (magnesium hydroxide). Magnesium in chlorophyll gives plants their green color.

13. Aluminum Ladder (Aluminum Al). Unlucky to walk under, and 13 isunlucky. Turquoise (blue-green) colored (turquoise is hydrated aluminum phosphate.

14. Silicon Chip (Silicon Si). It as 14 pins, and is the tan color of sand (silicon dioxide) or sandstone (silica).

15. Phosphorus Matches (Phosphorus P). Red/white striped book of 15,heads white, striker red (there are both white and red forms of phosphorus).The matches could light the dynamite (nitrogen) in the periodic table.

Atomic number 207

Atomic Number 20 Electron Configuration


16. Sulfuric Acid (Sulfur S). One pint (16 oz.), pale yellow in a flask.

What Is Atomic Number

17.Clorox (Chlorine Cl). Yellow-green bottle, the color of chlorine gas ('chloros' means yellow-green in Greek). Cleans 17 ways (Clorox is sodium hypochlorite). Note that Clorox has no letter 'h' making it easy to remember the abbreviation Cl.

Atomic Number 20 Calcium

18. Argon-filled Fluorescent Light (Argon Ar). 18-inch, sky-blue (air is 1% argon).

19. Kettle, or Pot of grayAshes (Potassium K).19th-century way to make soap from potash (potassium is named for potash, potassium carbonate or hydroxide,which is named for the pot of ashes used to obtain it).

20. Calcite Pearls (Calcium Ca). Ivory A string of 20 pearls. Calcite is a formof calcium carbonate.

Atomic Number Definition

Atomic Numbers21-4041-6061-8081-104
Back to John Pratt's Home Page