Answer:
3,4
Explanation:
Hydrogen has no other electron hence there is no screening of the valence electron by inner electrons. It is the lightest known element with a relative molecular mass of 2. Screening effect refers to the fact that inner or core electrons prevent the outermost electron from feeling the attractive force of the nucleus.
17.93 grams of oxygen gas occupy 12.3L of space at 109.4 kPa and 15.4°C. Details about how to calculate mass can be found below.
<h3>How to calculate mass?</h3>
The mass of a given gas can be calculated by multiplying the number of moles of the substance by its molar mass.
However, the number of moles of the gas must be calculated first as follows:
PV = nRT
Where;
- P = pressure = 1.0796941atm
- V = volume = 12.3L
- n = number of moles
- T = temperature = 288.4K
- R = gas law constant = 0.0821 Latm/molK
1.079 × 12.3 = n × 0.0821 × 288.4
13.27 = 23.68n
n = 13.27/23.68
n = 0.56mol
Mass = 0.56 × 32
mass of oxygen gas = 17.93g
Therefore, 17.93 grams of oxygen gas occupy 12.3L of space at 109.4 kPa and 15.4°C.
Learn more about mass at: brainly.com/question/19694949
Two protons and two neutrons are emitted and trapped as materials like uranium and thorium deep underground decay into radium and thorium, respectively. These alpha-particles transform into stable helium atoms as they take on electrons from their surroundings.
<h3>
What elements go through alpha decay?</h3>
Alpha decay usually occurs in heavy nuclei such as uranium or plutonium, and therefore is a major part of the radioactive fallout from a nuclear explosion.
<h3>
Where does alpha decay occur?</h3>
Alpha decay occurs most often in massive nuclei that have too large a proton to neutron ratio. An alpha particle, with its two protons and two neutrons, is a very stable configuration of particles.
Learn more about alpha decay here:
brainly.com/question/1898040
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Answer: 
Explanation:
Depression in freezing point is given by:
= Depression in freezing point
i= vant hoff factor = 1 (for non electrolyte like urea)
= freezing point constant = 
m= molality
Weight of solvent (X)= 950 g = 0.95 kg
Molar mass of non electrolyte (urea) = 60.06 g/mol
Mass of non electrolyte (urea) added = ?
Thus urea was dissolved.
