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What property is a characteristic of a substance that can be observed and does not change the identity of the substance

According to valence bond theory, which orbitals overlap in the formation of the bond in hf according to valence bond theory, which orbitals overlap in the formation of the bond in hf 2s on h and 2p on f 1s on h and 2s on f 1s on h and 1p on f 1s on h and 2p on f 1s on h and 3p on f

Give an example in which the electrical energy changes to light energy