What are the rules for writing the symbols of an elements

Hello!

Each element on the periodic table ALWAYS begins with an UPPERCASE letter, for example, hydrogen is written as H.

If the element has two letters, for example lithium, then the first letter is UPPERCASE, and the next letter is LOWERCASE. This is shown as Li.

If there's two or more elements (also known as a compound), (ex. sodium chloride), then it follows the same rules, the first letter is in UPPERCASE and next letter is LOWERCASE, but when a new element is introduced (in this case chlorine), the first letter is UPPERCASE and the next letter in LOWERCASE. Sodium is Na and Chlorine is Cl. As a compound it is NaCl, and it's name is sodium chloride.  

Basic rules:

it should have an internal chamber and two thermometers sticking out of the top. the internal chamber will also be closed off from the outside.

a. the law of proportion states the combination of 2 atoms in a specific ratio to produce multiple compounds such as the given statement of question ‘1st compound contains 88.8 % cu ’ indicates 88.8 g of cu is present along with 11.2 g oxygen in 100 g of compound whereas the statement ‘2st compound contains 79.9 % cu ’ indicates 79.9 g of cu is present along with 20.1 g oxygen in 100 g of compound

1st compound contains 88.8 g cu

for cu

m = 63 g /mol

atomic % = 88.8 /63 = 1.42

for o

m = 16 g /mol

atomic % = 11.2 /16 = 0.7

b. the emperical formula of 1st compound is

cu1.4o0.7

cu2o