Answer:
Element X is Arsenic (As)
Explanation:
- Elements in the periodic table are either metals, non-metals or metalloids.
- Metals are elements that react by losing electrons to obtain a stable configuration and form cation.
- Non-metals are those elements that react by gaining electrons to form a stable configuration and form anion.
- Metalloids are elements in the periodic table that have both metallic and non-metallic properties.
- Examples of metalloids include Selenium, Arsenic, Boron, etc.
- Arsenic is a metalloid in period 4 (four energy levels) with five valence electrons.
Answer:
D
Explanation:
The unit used to measure atomic mass is the atomic mass unit (amu). A single amu is equivalent to 1/12 the mass of an atom from the carbon-12 isotopIsotopes with different numbers of protons and neutrons will have an actual mass slightly different from the atomic mass calculated in atomic mass units.
Answer:
equal the number of electrons.
Explanation:
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.