What element has 21 neutrons, 20 electrons and 20 protons

Write the chemical symbols for three different atoms or atomic cations with 27 electrons. asap!

According to each substances heat of fusion, which of the items below requires more heat to be added per gram of substance to go from solid to liquid? silver sulfur water lead

Which is true of a liquid? it has a definite volume but not a definite mass.it has a definite mass but not a definite volume.it has a definite volume but not a definite shape.it has a definite shape but not a definite volume.