Can atoms lose electrons by themselves? I know atoms lose or gain electrons through ionic bonding but when they are by themselves do they lose electrons? I read in a book on metallic bonding which involves free electrons(the lost ones) and the ions itself. 
 A: If the atom is capable of $\beta$ + decay, then an electron might be lost after the event because the number of protons in the nucleus would have decreased by one. The tunneling to freedom idea in the comments is impossible because tunneling only happens when there is a finite potential barrier.
A: *

*You mean like a lone Hydrogen atom? Can the single electron in Hydrogen pack its bags and leave?

*Yes but only if it acquires the energy to leave, right? 
In this case the binding energy (due to the electromagnetic forces) in the ground state is $-13.6~\mathrm{eV}_,$ therefore if it somehow acquires this energy it will leave, forever!
There are different ways this exchange of energy can happen, a very simple scenario would be some high energy photon, or other particle (like another electron) scattering onto the electron and blowing it away.
In an empty Universe with nothing but a single Hydrogen atom, I'm afraid they will be stuck together forever!
A:  An atom that gains one or more electrons will have a NEGATIVE charge.
 An atom that loses one or more electrons will have a POSTIVE charge.
 An atom that gains or loses one or more electrons is called an ION.
 A positive ion is called a CATION and a negative ion is called an ANION. 
Atoms will transfer one or more electrons to another to form the ionic bond.
 Each atom is left with a complete outer shell.
 An ionic bond forms between a metal ion with a positive charge and a nonmetal ion with a negative
charge. 
