When am atom loses electron it becomes

It becomes an ion.

Orginally, the number of electrons of an atom should be same as the number of protons, and the atom should be electrically neutral, as each proton brings a positive charge and each electron brings a negative charge. However, when an atom loses or gains electrons, the charge would be positive or negative, depending on what the change is. In this way, the atom is no longer an atom, but an ion.

The number of electrons gained or lose by an atom depends on their group number in the periodic table. They'll gain or loose the least electrons in order to have an octet of electrons (or duplet). Which means, their outermost shell electrons would be 8, or 2 for the first shell.

One exam is fluorine. It is in the group VII, it has an outer most shell electron of 7. In order to make fluoride ion, one electron is gained, so that the outer most shell will have 8 electrons. Therefore, fluoride ion has a negative charge, as one electron brings a negative charge.

assuming that your periodic table has eighteen columns, you should highlight   the four elements in the third column from the left of the table.

explanation

neutral atoms of elements after calcium contain d electrons. the energy of d orbitals of a particular main shell lies between the energy of the s and p orbitals of the next main shell. for example, electrons in the have energy higher than those in the orbital while lower than those of the orbital.

by the aufbau principle, electrons fill orbitals one at a time, starting from those of the lowest energy. the orbital is therefore filled right after orbitals and before orbitals.  

potassium has electron configuration and calcium . the s orbital of a main shell holds a maximum of two electrons. the next element would thus have the electron configuration and satisfy the requirements.

a neutral atom of the element contains three electrons on top of the most recent noble gas element. it should thus be placed in the third column of the periodic table. both scandium and yttrium would satisfy the conditions. an aufbau diagram indicates that the 4f orbital is filled before the 5d. however, it appears that exceptions exists for both lanthanum and actinium. neutral atoms of the two d-block elements also demonstrate the and should be highlighted as well.

Hno3(aq) → h+(aq) + no3−(aq). picture ii best represents the strong acid hno3. strong acids are strong electrolytes