Question

Why electron can not present in side the nucleus?

Answer 1

That answer includes some deadass quantum physics,you sure you gonna understand?

Answer 2

the nucleus contains neutrons and protons and protons are positively charged while neutrons are having no charge. so nucleus is a completely positively charged body. the electrons are negatively carved body which move in their elliptical orbits around the nucleus. if electrons would fall into nucleus the atom would collapse