John Dalton was a scientist who proposed that all matter consists of atoms. At this stage, no one had yet discovered neutrons and the nucleus. As a result, Dalton's model consisted of a single atom i.e. the atom was the smallest object.
A mass spectrometer is an instrument that is able to see what is inside an atom. Scientists have been able to prove that the item is not the smallest object in the world. Atoms are made up of smaller objects called protons, neutrons and electrons.
We can, therefore, safely conclude that data from mass spectrometry has helped modern scientists to make modifications to Dalton's model. <span>
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Thus BeF2 is of most covalent character.
Anyways, covalent/ionic character is a bit tricky to figure out; we measure the difference in electronegativity of two elements bonding together and we use the following rule of thumb: if the charge is 0 (or a little more), the bond is non-polar covalent; if the charge is > 0 but < 2.0 (some references say 1.7), the bond is polar covalent; if the charge is > 2.0 then the bond is ionic. Covalent character refers to smaller electronegativity difference while ionic character refers to greater electronegativity difference.
Now, notice all of our bonds are with F, fluorine, which has the highest electronegativity of 3.98. This means that to determine character we need to consider the electronegativities of the other elements -- whichever has the greatest electronegativity has the least difference and most covalent character.
Na, sodium, has electronegativity of 0.93, so our difference is ~3 -- meaning our bond is ionic. Ca, calcium, has 1.00, leaving our difference to again be ~3 and therefore the bond is ionic. Be, beryllium, has 1.57 yielding a difference of ~2.5, meaning we're still dealing with ionic bond. Cs, cesium, has 0.79, meaning our difference is again ~3 and therefore again our compound is of ionic bond. Lastly, we have Sr, strontium, with an electronegativity of 0.95 and therefore again a difference of roughly 3 and an ionic bond.
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The first blank is a compound, second is a mixture
Niels Bohr is the first person to describe a chemical reaction as the combination of atoms.
The reaction is incorrect. The correct reaction is: Na₂SO₄ + Hg(NO₃)₂ → HgSO₄ + 2NaNO₃. The options are:
A. Hg₂SO₄
B. Na₂SO₄
C. Na⁺
D. NO₃⁻
E. SO₄⁻²
F. Hg₂(NO₃)₂
G. NaNO₃
H. Hg⁺²
Answer:
C, D, E, H
Explanation:
The ions are formed after dissociation of the compound in the solution. When they're negatively charged, they're called anions, when they're negatively charged, they're called cations. If the ion is presented on both sides of the reaction, it is called a spectator ion.
Thus, the reaction given:
Na₂SO₄ + Hg(NO₃)₂ → HgSO₄ + 2NaNO₃
So, let's do the dissociation.
Na₂SO₄ is formed by the ions Na⁺ and SO₄⁻²;
Hg(NO₃)₂ is formed by the ions Hg⁺² and NO₃⁻;
HgSO₄ is formed by the ions Hg⁺² and SO₄⁻²;
NaNO₃ is formed by the ions Na⁺ and NO₃⁻.
Thus, the spectator ions are Na⁺, SO₄⁻², Hg⁺², and NO₃⁻.
