how to remember the atomic mass of first 20 elements?

Answer 1

I never and I taught many years of chemistry. However, rule of thumb is that for the first 20 elements. the atomic mass is usually about 2 times the atomic number. He (atomic number = 2, atomic mass = 4), C (6, 12), N (7, 14), O (8, 16), Ne (10, 20), etc.

Answer 2

Atomic Structure First 20 Elements

Answer 3

Mass of any element is the sum of mass of proton(s) + mass of Neutrons + other building blocks like electrons. Hydrogen has only one proton and one electron, so its mass number is 1, but Mass is slightly higher then 1. If you are using atomic mass for not very specific purposes, and need not very accurate values - you can take it as 1. Most elements with small number of protons have almost equal number of neutrons. For first 20 elements you can remember it easily or - elements with even atomic numbers usually have a mass number is exactly double the atomic number, e.g. Helium-4, Carbon-12, Oxygen-16, Neon-20, Magnesium - 24, Sulphur -32, calcium-40.The main exception to this is Argon mass = 40 for atomic number 18.
As elements with odd number of protons need one or two extra neutron to overcome repealing force of protons within the nuclei, therefore most elements with odd atomic numbers have a mass 1(or 2 or 3 in some Case) more than double the atomic number, e.g. Aluminium - 27, phosphorus -31, lithium - 7, beryllium -9, sodium -23, chlorine 35 (and 36, both the isotopes are almost in equal proportion)
The main exceptions to this are nitrogen - atomic number 7, mass = 14, potassium (41 for 19) and chlorine atomic number 17, mass = 35 and 36, average is 35.5.

Answer 4

Hydrogen is 1 of course.

The easy way to remember is this:
* elements with even atomic numbers usually have a mass number (of the most abundant isotope) exactly double the atomic number, e.g. Helium-4, Carbon-12, Oxygen-16, Neon-20, Magnesium - 24, Sulphur -32, calcium-40 etc.
* elements with odd atomic numbers have a mass 1 more than double the atomic number, e.g. Aluminium - 27, phosphorus -31, lithium - 7, beryllium -9, sodium -23 etc

The main exceptions to this rule are nitrogen (atomic number 7, mass = 14), Argon (mass = 40 for atomic number 18) and potassium (41 for 19).

Hope that helps!

Answer 5

up to 20elements atomic mass is twice of atomic number but exception few elements there are HYDROGEN atom no is mass no because absence of neutron after multiplying with 2 if atom no is odd no add with one, no need add one if it is even no. nitrogen, chlorine are the special carbon 6 * 2 =12 , OXYGEN 8* 2 = 16 ,Ne 10 * 2 =20 Na 11 * 2 = 22 + 1 =23 Mg 12 * 2 =24 Cl 17 * 2 = 34 + 1 = 35 N 7 * 2 =14*

Answer 6

I have a trick whose atomic number is even we should do double whose atomic number is odd we should do double and add 1 this is only up to 20 and there are exceptions=Belated,N&H

Answer 7

Like three phone numbers

Answer 8

Relate it with ur daily life,u can remember it.

Answer 9

oops... thts little difficult dear

stil go to the foll link...
best of luck!!!!!

Answer 10

make up a story about them, thats what i did