Electrons in an atom can be classified as core electrons and valence electrons. Valence electrons are those electrons which are present in valence shell and participates in bond formation. While, Core electrons are all remaining electrons which are not present in valence shell, hence not take part in bonding.
Atomic number of Selenium (Se) is 34 hence it has 34 electrons with following electronic configuration;
1s², 2s², 2p⁶, 3s², 3p⁶, 4s², 3d¹⁰, 4p⁴
From electronic configuration it is found that the valence shell is 4, and the number of electrons present in valence shell are 6. So,
Core Electrons = Total Electrons - Valence Electrons
Core Electrons = 34 - 6
Core Electrons = 28
Result:
There are 28 core electrons in Selenium.
Answer:
mass of HCl = 3.65 g
Explanation:
Data Given:
Moles of hydrochloric acid HCl = 0.1 mole
Mass in grams of hydrochloric acid HCl = ?
Solution:
Mole Formula
no. of moles = Mass in grams / molar mass
To find Mass in grams rearrange the above Formula
Mass in grams = no. of moles x molar mass . . . . . . . (1)
Molar mass of HCl = 1 + 35.5 = 36.5 g/mol
Put values in equation 1
Mass in grams = 0.1 mole x 36.5 g/mol
Mass in grams = 3.65 g
mass of HCl = 3.65 g
Answer:
A sample of an ideal gas has a volume of 2.21 L at 279 K and 1.01 atm. Calculate the pressure when the volume is 1.23 L and the temperature is 299 K.
You need to apply the ideal gas law PV=nRT
You have the pressure, P=1.01 atm
you have the volume, V = 2.21 L
The ideal gas constant R= 0.08205 L. atm/ mole.K at 273 K
find n = PV/RT = (1.01 atm x 2.21 L / 0.08205 L.atm/ mole.K x 273 K)
n= 0.1 mole, Now find the pressure for n=0.1 mole, T= 299K and
L=1.23 L
P=nRT/V= 0.1mole x 0.08205 (L.atm/ mole.K x 299 k)/ 1.23 L
= 1.994 atm
Explanation:
According to florida wildlife group who experimentally tape magnets to crocodile heads to disrupt their homing ability so they don't wander into residential areas
Answer:
Distillation
Explanation:
By using the method of distillation we'll identify if there is other properties of liquid by looking the temperatures,the ordor or the boiling point.
