Questions

When atoms react they do so in order to reach the lowest energy, which is the most stable. The electrons orbitals will overlap in the way that reduces the energy the most. Orbitals of similar energy will produce the greatest stabilisation.The answer you gave isn't the whole story, it depends what species is reacting with what. The effective nuclear charge on the atom will affect the energy of the valance electrons.

Hence, the reactivity of an atom arises from the existence of unpaired electrons in the valence shell.

If as a business, you buy goods or services on credit from a supplier (accounts payable) then the supplier will supply the goods and business will incur a liability to the supplier for that amount, but no cash will change hands at that stage.

Some of those shop keepers allowed regular "trustworthy" customers to purchase items without having the full payment.

Hence, Buying on credit means that no actual money has changed hands.

M.F.Hussain

Microwaves are high-frequency signals in the 300 MHz to 300 GHz range. This is in contrast to radio signals, which are typically broadcast in all directions. Radio signals operate in the 3 Hz to 300 MHz range.

Microwave signals are used for both satellite and ground-based communications.