What is the name of the element with a valence electron configuration of 4s^2

Which term refers to a property that depends only on the amount of a substance? ©@

Which supports the idea that birds and butterflies both have wings but they do not have a common ancestor with wings? a. the wings are analogous structures that evolved differently and do not have a similar internal structure. b. the wings are homologous structures that evolved differently and do not have a similar internal structure. c. wings of birds are vestigial structures, but the wing structures of bats are not vestigial. d. wings of bats are vestigial structures, but the wing structures of birds are not vestigial

In the reaction between a crushed antacid tablet and vinegar what gas is emitted