Wiktionary (0.00 / 0 votes) Rate this definition: floater (Noun) Agent noun of float; one who floats. floater (Noun) An employee of a company who does not have fixed tasks to do but fills in wherever needed, usually when someone else is away. floater (Noun)
25Mn-55 (the naturally occurring isotope) has 25 protons, 25 electrons and 30 neutrons, 25Mn-54 has 29 neutrons instead but is not a stable isotope. 25Mn-55 (the naturally occurring isotope) has 25 protons, 25 electrons and 30 neutrons, 25Mn-54 has 29 neutrons instead but is not a stable isotope.
Obviously atomic number = no of protons = total number of electrons in an atom. Sodium 2,8,1 (1s1 2s2 2p6 3s1) has 13 electrons and is a group 1 element so has 1 valence electron (1 electron in outer shell). So 12 core and 1 valence.