Helium - 4 isotope has 2 protons and 2 neutrons.
Its atomic number is 2 (the number of protons). Atomic number is the number of protons in the atom of an element and it identifies the element. All the isotopes of an element have the same atomic number (same number of protons). So, all the isotopes of hellium have 2 protons.
The number 4 that identifies the helium - 4 isotope is the mass number, i.e. the number of protons plus the number of neutron. So, helium-4 isotope has 2 protons and 2 neutrons. While, other isotopes of helium have 2 protons but different number of neutrons.
The atomic number enable us to deduce the number of electrons in an atom because the atoms are neutral, which implies that the positive and negative charge are equal. Given that the magnitude of the charge of electons and protons are equal but the sign is opposed (protons are positve and electrons are negative) the number of electrons in the atom equals the number of protonts. That is why the atomic number is also the number of electrons of the atom.
Answer:
On the periodic table, electronegativity generally increases as you move from left to right across a period and decreases as you go down a group. As a result, the most electronegative elements are found on the top right of the periodic table, while the least electronegative elements are found on the bottom left.
Explanation:
Answer:
1, 2, 4
Explanation:
The primitive cubic unit cell has eight corners, and each corner is shared with 8 cubic unit cells. Therefore since we have one atom at each corner, we will have:
8 corner x 1 atom/8 corner = 1 atom
There is then the equivalent of one atom per unit cell in the primitive cubic cell.
For the body-centered cubic unit cell, we have 8 corners again shared each by 8 lattices as in the simple cubic plus we have one atom in the center of the cubic lattice. Therefore, the number of atoms in the body -centerd unit cell is two:
8 corner x 1 atom/8 corner = 1 atom
+
1 atom in the center
= 2 atoms/ unit cel
For the face-centerd cubic again we have 8 atoms in the corners shared by 8 lattices, plus 1 atom in each of the faces shared by two unit cells:
8 corner x 1/8 atom/corner + 6 faces x 1 atom/face = 4 atoms/unit cell
47% yield.
First, let's determine how many moles of ethane was used and how many moles of CO2 produced. Start with the respective atomic weights.
Atomic weight carbon = 12.0107
Atomic weight hydrogen = 1.00794
Atomic weight oxygen = 15.999
Molar mass C2H6 = 2 * 12.0107 + 6 * 1.00794 = 30.06904 g/mol
Molar mass CO2 = 12.0107 + 2 * 15.999 = 44.0087 g/mol
Moles C2H6 = 8 g / 30.06904 g/mol = 0.266054387 mol
Moles CO2 = 11 g / 44.0087 g/mol = 0.249950578 mol
Looking at the balanced equation, for every 2 moles of C2H6 consumed, 4 moles of CO2 should be produced. So at 100% yield, we should have 0.266054387 / 2 * 4 = 0.532108774 moles of CO2. But we only have 0.249950578 moles, or 0.249950578 / 0.532108774 = 0.46973587 =
46.973587% of what was expected.
Rounding to 2 significant figures gives 47% yield.
Answer:
Explanation:
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In this case, according to the following chemical reaction we found on goo gle as it was not given:
Whereas we can see a 2:4 mole ratio of potassium permanganate product to potassium hydroxide reactant with molar masses of 158.03 g/mol and 54.11 g/mol respectively. In such a way, by developing the following stoichiometric setup, we obtain the mass of KOH to start with:
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