2.
The atomic number which is 2 stands for how many protons (also electrons, in an uncharged atom) are in the element's atom.
8
Helium has two electrons. You can tell from looking at the periodic table because; each element has the same number of electrons as protons (the number of protons is the atomic number, which increases in number as you move from left to right across the periodic table, starting with one at Hydrogen).
There are 2 elements in the first period of the periodic table: Hydrogen and Helium.
There are 2 electrons in level one of a helium atom.
Calcium has 20 electrons
2.You are in terrible need of a periodic table. It's really not that difficult, and it's well worth learning.
The d block of the periodic table contains 10 valence electrons.
period 3 elements in the periodic table have 3 electrons in there outher shell hence the name.
Xenon has 54 electrons.
Each element has a specific number that doesn't change. That number is the atomic number they are given on the periodic table. For example Hydrogen has 1 electron, Helium has 2, Lithium has 3, and so on. The number of electrons in a atom would be determined by what ever element it is.
Chlorine has 17 electrons. It is displayed as atomic number in periodic table.
Helium atoms only need 2 valence electrons to have a filled outermost energy level because helium is in the first period of the periodic table and its outermost energy level can only hold a maximum of 2 electrons.