Answer:
<h3>... :-!...................nose...........</h3>
1. rancidification fixation of water is CHEMICAL CHANGE
2. Tearing of paper is PHYSICAL CHANGE
3. Rusting if iron is CHEMICAL CHANGE
4. Electrolysis of water is CHEMICAL CHANGE
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.
<span>
</span>
Answer:
I remember doing this in 7th,
1. D
2. B or D, more leaning on B though
3. A
Answer:
Electrons do not follow circular orbits around the nucleus
Explanation:
Bohr's model of the atom is a combination of elements of quantum theory and classical physics in approaching the problem of the hydrogen atom. According to Neils Bohr, stationary states exist in which the energy of the electron is constant. These stationary states were referred to as circular orbits which encompasses the nucleus of the atom. Each orbit is characterized by a principal quantum number (n). Energy is absorbed or emitted when an electron transits between stationary states in the atom.
Sommerfeld improved on Bohr's proposal by postulating that instead of considering the electron in circular orbits, electrons actually orbited around the nucleus in elliptical orbits, this became a significant improvement on Bohr's model of the atom until the wave mechanical model of Erwin Schrödinger was proposed.
