Periodic table

how are elements organized on the periodic table? Select all that apply. 1. Into periods or horizontal rows that share a pattern 2. By order of relative abundance of the element on Earth 3. into order of densities from lowest to highest 4. into vertical groups of elements that have similar physical and chemical properties 5. by increasing order of atomic number

1,3,4

Mendeleev made the first periodic table around _____.

1870

The atomic mass of F is 9 10 19 55

19

F has ___ valence electrons

7

F is the symbol for the element

Fluorine

Mendeleev saw trends in the physical and chemical properties of elements when he organized them by _____.

atomic weight

where do you find elements grouped that have the most similar physical and chemical properties?

in vertical groups or families.

The gaps on Mendeleev's table _____.

represented elements not discovered in his time