An element has 4 protons, 5 neutrons, and 4 electrons. what is the atomic mass of the element? 4 5 8 9

at mass = protons+neutrons=9

9

Explanation:

The atomic mass is defined as the sum of number of protons and the neutrons.

The atomic number is defined as the number of protons in the nucleus.

Here, the number of protons are 4

the number of neutrons are 5

So the sum of number of protons and neutrons = 4 + 5 = 9

Thus, the atomic mass of the element is 9.

  the grams     of oxygen gas   that can be produced     is 20.6   grams of o₂

calculation

2liclo₃ →   2 licl + 3 o₂

step 1:   find the moles of liclo₃

moles = mass÷ molar mass

from periodic table the molar mass of liclo₃ =6.9 +35.5   +(16 x3) =90.4 g/mol

moles=38.7 g÷90.4 g/mol=0.4281   moles

step 2:   use the   mole ratio   to calculate the moles of o2

from equation above, liclo₃: o₂   is 2: 3  

therefore the moles of   o₂=0.4281 moles x3/2 =0.6422   moles

step 3: find mass   of o₂

mass= moles x molar mass

from periodic table the   molar mass of   o₂ = 16 x2= 32 g/mol

mass=0.6422   moles   x   32 g/mol = 20.6 grams of o₂