Chemical properties is when a material undergoes a chemical change or reaction like a nail rusting and a physical change can be observed without changing the material like temperature, color, texture, odor,etc.
Answer:
4
Explanation:
Relationship between wavenumber and Rydberg constant (R) is as follows:

Here, Z is atomic number.
R=109677 cm^-1
Wavenumber is related with wavelength as follows:
wavenumber = 1/wavelength
wavelength = 253.4 nm

Z fro Be = 4

Therefore, the principal quantum number corresponding to the given emission is 4.
An electron can be added to halogen atom to force a halide ion with 8 valence electrons
<h3>What is an atom?</h3>
An atom can be defined as the smallest part of an element which can take part in a chemical reaction.
However whenever, an electron is added to halogen atom to force a halide ion with 8 different valence electrons
So therefore; an electron can be added to halogen atom to force a halide ion with 8 valence electrons
Learn more about halogens:
brainly.com/question/18276987
#SPJ1