The element that has a valence configuration of 2s2 is

The element having given valence electronic configuration is beryllium.

Explanation:

Electronic configuration is defined as the representation of electrons around the nucleus of an atom. Number of electrons in an atom are determined by the atomic number of that atom.

Valence electrons are defined as the electrons present in the outermost shell of an atom.

We are given:

Valence electronic configuration of an atom =

So, the actual electronic configuration of atom will be

Total number of electrons = 2 + 2 = 4

So, the atomic number of given element is 4 and the element is beryllium

Hence, the element having given valence electronic configuration is beryllium.

14 days is the half-life of phosphorus-32

it can be observed without changing the identity of the object.

it depends on what substance you're talking about as well as many other factors. in quantum mechanics, the observation of particles affects the observers ability to measure certain properties. for example: you can know the velocity of a particle, but you can't know it's position; or you can know it's position, but not it's velocity. it's like trying to find out where a grain of sand is by throwing other grains of sand at it. once you find out where it is, it's been moved. it's also like trying to find an answer to the question of whether or not a tree falling in a forest makes a sound if nobody is there to hear it. paradoxically, the only way to find out is to be there and hear it.