Chemistry 2 Marks Questions

→ The actinoid metals are all silvery in appearance but display a variety of structures. The structural variability is obtained due to irregularities in metallic radii which are far greater than in lanthanoids.
→ The magnetic properties of the actinoids are more complex than those of the lanthanoids.
→ It is evident from the behaviour of the actinoids that the ionization enthalpies of the early actinoids, though not accurately known, but are lower than for the early lanthanoids.
→ The stable oxidation state of all the lanthanoids is (+3). In actinoids, oxidation states (+2) to (+6) are seen.
→ In lanthanoids only promethium is radioactive but all the actinoids are radioactive.

→ Use of the lanthanoids is for the production of alloy steels for plates and pipes.
→ A well known alloy is mischmetal which consists of a lanthanoid metal (~95%) and iron (~5%) and traces of S, C, Ca and Al.
→ A good deal of mischmetal is used in Mg-based alloy to produce bullets, shell and lighter flint.
→ Mixed oxides of lanthanoids are employed as catalysts in petroleum cracking.
→ Some individual Ln oxides are used as phosphors in television screens and similar fluorescing surfaces.

→ All the lanthanoids are silvery white soft metals and tarnish rapidly in air.
→ The hardness increases with increasing atomic number, samarium being steel hard.
→ Their melting points range between 1000 to 1200 K but samarium melts at 1623 K.
→ They have typical metallic structure and are good conductors of heat and electricity.
→ Density and other properties change smoothl except for Eu and Yb and occasionally for Str and Tm.

→ The f-block consists of the two series, lanthanoids (the fourteen elements following lanthanum) and actinoids (the fourteen elements following actinium).
→ Because lanthanum closely resembles the lanthanoids, it is usually included in any discussion of the lanthanoids for which the general symbol Ln is often used.
→Similarly, a discussion of the actinides includes actinium besides the fourteen elements constituting the series.
→ The lanthanoids resemble one another more closely than do the members of ordinary transition elements in any series.
→ They have only one stable oxidation state and their chemistry provides an excellent opportunity to examine the effect of small changes in size and nuclear charge along a series of otherwise similar elements.
→ The chemistry of the actinoids is, on the other hand, much more complicated. The complication arises partly owing to the occurrence of a wide range of oxidation states in these elements and partly because their radioactivity creates special problems in their study.

→ The manganate and permanganate ions are tetrahedral

→ The green manganate is paramagnetic with one unpaired electron but the permanganate is diamagnetic.
→ The π-bonding takes place by overlap of p orbitals of oxygen with d orbitals of manganese.

→ The transition elements have high enthalpy of atomization because of presence of strong bonds between the atoms.
→ The enthalpy of atomisation increases with the increase in number of unpaired electrons which results in formation of strong bonds due to strong interatomic interactions.
→ The metals of the second and third series have greater enthalpies of atomisation than the corresponding elements of the first series; this is an important factor in accounting for the occurrence of much more frequent metal - metal bonding in compounds of the heavy transition metals.

ty → All the transition elements are metallic element.
→ All the transition metals have high tensile strength, ductility, malleability, high thermal and electrical conductivity and metallic lustre.
→ With the exceptions of Zn. Cd. Hg and Mn, they have one or more typical metallic structures at normal temperatures.

Sc	Ti	V	Cr	Mn	Fe	Co	Ni	Cu	Zn
hcp (bcc)	hcp (bcc)	bcc	bcc (bcc,ccp)	X (hcp)	bcc (hcp)	ccp	ccp	ccp	X (hcp)
Y	Zr	Nb	Mo	Te	Ru	Rh	Pd	Ag	Cd
hcp (bcc)	hcp (bcc)	bcc	bcc	hcp	hcp	ccp	ccp	ccp	X (hcp)
La	Hf	Ta	W	Re	Os	Ir	Pt	Au	Hg
hcp (ccp,bcc)	hcp (bcc)	bcc	bcc	hcp	hcp	ccp	ccp	ccp	X

(bcc body centred cubic; hcp = hexagonal close packed;
ccp = cubic close packed; X = a typical metal structure).
→ The transition metals (with the exception of Zn, Cd and Hg) are very much hard and have low volatility.
→ Their melting and boiling points are high.

→ The d-block occupies the large middle section flanked by s- and p-blocks in the periodic table.
→ The name 'transition' given to the elements of d-block is only because of their position between s- and p-block elements, and their properties is transition between s and p block elements.
→ The d-orbitals of the penultimate energy in their atoms receive electrons giving rise the three rows of the transition metals, ie., 3d, 4d and 5d.
→ The fourth row of 6d is still incomplete.

→ The element in which last electron fill in f-orbital is known as f-block element.
→ f-block element is known as inner transition element.
→ The elements constituting the f-block are those in which the 4f and 5f orbitals progressively filled.
→ The two series of the inner transition metals, (4f and 5f) are known as lanthanoids and actinoids respectively.

→ The d-block of the periodic table contains the elements of the groups 3-12 in which the d orbitals are progressively filled in each of the four long periods.
→ The name transition metals is often used to refer to the elements of d-block
→ There are mainly three series of the transition metals, 3d series (Sc to Zn), 4d series (Y to Cd) and 5d series (La and Hf to Hg).
→ The fourth 6d series which begins with Ac is still incomplete.