Locate the row containing lithium (Li), sodium (Na), potassium (K), rubidium (Rb), and cesium (Cs). Look up these elements in the periodic table, and click each element to reveal its properties. Explain why Mendeleev might have grouped these elements together.

1. a)c-14 has two more protons

2. d)they have different numbers of protons, neutrons, and valence electrons; they are all gases at room temperature.

3. c) iron and nickel.

the transfer of heat by electromagnetic radiation is called thermal radiation . it is usually carried out by electromagnetic waves in an energy range just below the visible spectrum, which is the infrared range.

so the answer would be radiation.

: )

you need to have a picture of the atom that way we can answer it