An atom of titanium, with the symbol Ti, represents an element found in the periodic table. Titanium, with atomic number 22, is known for its strength, low density, and resistance to corrosion. It has an electron configuration of [Ar] 3d2 4s2, which is pivotal in its chemical behavior and bonding characteristics. Notably used in aerospace, medical implants, and even in pigments (as titanium dioxide), titanium's versatile properties stem from its atomic structure. It readily reacts with oxygen, forming a passive oxide layer that protects it from further corrosion. Given its abundance in the Earth's crust, it's essential in various industries, yet its extraction process, particularly from ilmenite and rutile ores, underlines the balance between utility and environmental impact.

Connecting PVC to cast iron sewer pipe underground involves the use of a flexible coupling, known as a no-hub or shielded coupling. This connector is designed to join these dissimilar materials, ensuring a secure and leak-proof connection. First, you need to clean the end of the cast iron pipe, removing any rust or debris. Similarly, prepare the PVC pipe end to ensure it's smooth and free from burrs. Slide the flexible coupling over the end of the PVC pipe, then insert the PVC end into the cast iron pipe. Slide the coupling over the junction where the pipes meet, ensuring it covers both pipes equally. Tighten the clamps on both ends of the coupling with a screwdriver or a wrench. This method is widely accepted in plumbing practices and adheres to most local building codes. However, always consult with local regulations to ensure compliance.

Polypropylene is a versatile plastic with a wide array of uses due to its resistance to fatigue, most chemicals, and high melting point. Common items made from it include packaging, textiles (such as ropes, thermal underwear, and carpets), automotive parts (bumpers, battery cases), and consumer goods like plastic containers and reusable water bottles. Additionally, its high resistance to electricity makes it ideal for electronic components. In the medical field, polypropylene is used for syringes, medical vials, and as a material in surgical sutures. The material is appreciated for being lightweight, durable, and recyclable, contributing to its popularity in various industries.