Answer:
He developed the concept of concentric electron energy levels
Explanation:
Before Bohr's model, Rutherford's model was proposed. This model explains most of the properties of the atom but failed to explain the stability of the atom.
As per Rutherford's model, electrons revolve around the nucleus in the orbit.
But revolving electron in their orbit around nucleus would give up energy and so gradually move towards the nucleus and therefore, eventually collapse.
Bohr's proposed that the electrons around the nucleus move orbit of fixed energy called "stationary states". Electrons in these stationary states do not radiate energy.
Therefore, proposal of concentric electron energy levels refine the atomic models.
Answer:
4) Van der waals forces
Explanation:
Krypton (Kr) belongs to the noble gas group and has fully filled valence orbitals. In the solid phase, Kr exists as a white solid with a face centered cubic structure.
Intermolecular forces of attraction from the strongest to the weakest include:
Ionic > hydrogen bonding > dipole-dipole > london dispersion
Kr is monoatomic and non-polar. When fully filled (stable) valence orbitals of 2 Kr atoms approach each other in close proximity they experience a repulsive force which prevents the formation of strong bonds. Thus, the only force of attraction in Kr is the long range weak Van Der Waals force also known as the london dispersion force.
Answer:
No this statement is false.
Explanation:
when an atom lose or gain the electron ions are formed. If the atom lose an electron the positive ions are formed called cations while anion is formed by the gaining of electron by an atom The elements having less electrons in valance shell usually lose their electrons while the elements like halogens having 7 valance electrons gain an electron to complete the octet. while p block elements noble gases are inert, their outer most valance shell is complete so they do not form ions.
P block elements are non-metals, metals and metalloids. These are thirty five elements. The P-block elements are present on right side of periodic table. There valance electrons are present in P orbital. The p-block metals are shiny and good conductor of heat and electricity. These metal lose the electron which is accept by non metals and form ionic bond. They have high melting points.
Metalloids includes boron, silicon, germanium, arsenic, antimony and tellurium. Metalloids contain both the properties of metals and non metals, Some metalloids are toxic like arsenic.
Most of p-block elements are non metals. They are bad conductor of heat and electricity and have low boiling points. The non metals mostly accept the electron from the metals and usually from ionic bond like in case of chlorine. It form the ionic compound with sodium.
The sodium chloride which is an ionic compound, formed by the complete transfer of electron from sodium to chlorine atom and form ionic bond. In this ionic compound sodium carry positive charge and chlorine carry negative charge there is attraction between these oppositely charged atoms.
