Which of the following is the most recent addition to the accepted model of the atom?

atoms are indivisible particles.
protons are located in the nucleus.
electrons form a cloud around the nucleus.
neutrons orbit the nucleus along circular paths.

Explain which group an element with the electron configuration 1s2 2s2 2p6 3s2 3p6 3d1 4s2 belongs to.

The mass of a neutron is equal to the mass of a proton plus the mass of an electron. true or false false true

6. using 3 – 4 sentences explain (in your own words) why water expands when it freezes? 7. using your knowledge of colligative properties explain whether sodium chloride or calcium chloride would be a more effective substance to melt the ice on a slick sidewalk. use 3 – 4 sentences in your explanation.