Which symbol correctly represents an element (d) whose atoms contain 15 protons and 20 neutrons?

Which object forms when a supergiant runs out of fuel? a red giant a black hole a white dwarf a neutron star

What does x represent in the formula for the compound xcl4?

13. a covalent bond between two atoms is likely to be polar if: a. one of the atoms is much more electronegative than the other. b. the two atoms are equally electronegative. c. the two atoms are of the same element. d. the bond is part of a tetrahedrally shaped molecule. e. one atom is an anion.