The multi-part identifier "Item_Master.ID" could not be bound.

I am Joining 2 table Purchase and Item_Master error occurred
Join query
select ItemID,PurchaseID from Purchase JOIN Unit ON Purchase.ItemID = Item_Master.ID JOIN Brand ON Purchase.VenderID = vendor_master.ID error
Msg 4104, Level 16, State 1, Line 3 The multi-part identifier "Item_Master.ID" could not be bound. Msg 4104, Level 16, State 1, Line 4 The multi-part identifier "vendor_master.ID" could not be bound. tables script
Purchase
CREATE TABLE [dbo].[Purchase]( [PurchaseID] [int] IDENTITY(1,1) NOT NULL, [ItemID] [int] NOT NULL, [Quantity] [int] NOT NULL, [VenderID] [int] NOT NULL, [Date] [date] NOT NULL, CONSTRAINT [PK_Purchase] PRIMARY KEY CLUSTERED ( [PurchaseID] ASC )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRI ...